The ratio of acid to base that is required to prepare a buffer with a pH of 4.0 using the conjugate pair hcooh/hcoo-1of (k_a = 1.78 x 10-4) is [HCOOHI]/[IHCOO-] = 3.99.
How to prepare buffer solution?
A buffer solution is a solution of a weak acid or base along with its salt. The main function of the buffer solution is to retain the pH value of the solution almost constant, even if a small quantity of a strong acid or base is added to it. The formula for buffer solution is BH+ + A-.
The ratio of the concentrations of conjugate acid and base species in a buffer solution is called buffer capacity.
It measures how much of an acid or base can be added to a solution before a significant change in pH occurs. The ideal buffer pH range is within 1 pH unit of the dissociation constant (pKa).
pH = pKa + log [A-] / [HA]
In this question, the given pH is 4.0 and the given pKa is 1.78 x 10-4.
Now, substituting these values in the above equation, we get pH = pKa + log [A-] / [HA]. 4.0 = -log1.78 x 10-4 + log [A-] / [HA] 4.0 + 4.25 = log [A-] / [HA]
Antilog of both sides to eliminate the logarithm from the right side of the equation
101.25 = [A-] / [HA]A- / HA = 101.25[HA] = A- / 101.25Ratio = HA / A-= [HA] / [A-]= 1 / 101.25= 0.0099= 1 / 101
Therefore, the required ratio of [HCOOHI] to [IHCOO-] is [HCOOHI] / [IHCOO-] = 3.99.
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numerically speaking is the rate of disappearance of reactants always the same number as the rate of the appearance of products?
Numerically speaking, the rate of disappearance of reactants is not always the same number as the rate of the appearance of products.
The reason behind it is that in a chemical reaction, both reactants and products are involved. Reactants transform into products over time, and this transformation is measured by the rate of reaction. The rate of reaction may be determined by the rate at which reactants disappear or products appear. However, the rate of disappearance of reactants may not be equal to the rate of appearance of products numerically because different numbers of moles of reactants and products may be involved in the chemical reaction. As a result, the stoichiometric coefficients of the reactants and products in the chemical equation play an important role in determining the rate of disappearance of reactants and the rate of appearance of products.
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Obi is trying to determine if a powdery, solid substance is an element or a compound. After recording some observations, he strongly heats a sample of the solid over a burner flame. After fifteen minutes, he turns off the flame and allows the sample to cool. He records his final observations in the data table. Which is the best explanation of his results? The heating changed some of the sample to gas, causing the mass to decrease without breaking down the sample. Therefore, the original sample is a compound. The appearance stayed the same, showing that the sample was not broken down by heating. Therefore, the original substance is an element. The mass decreased during heating and some of the impurities escaped. Therefore, the original substance is an element. The chemical reaction with acid changed, showing that the sample was broken down by heating. Therefore, the original substance is a compound
Since an element only contains one type of atom and cannot be divided into simpler substances using physical or chemical processes, it is most probable that the sample is an element.
The best explanation of Obi's results is that the appearance stayed the same, showing that the sample was not broken down by heating.
Therefore, the original substance is an element. When a substance is heated, it can undergo different types of changes depending on its composition. In this case, since the appearance of the sample did not change after heating, it indicates that the sample did not break down into simpler substances.
Therefore, the sample is most likely an element, since elements are composed of only one type of atom and cannot be broken down into simpler substances by physical or chemical means.
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The best explanation of Obi's results is: The appearance stayed the same, showing that the sample was not broken down by heating. Therefore, the original substance is an element.
If the appearance of the sample remained the same after heating, it indicates that the sample did not undergo any chemical changes and did not decompose into simpler substances. This suggests that the sample is an element, which is a pure substance made up of only one type of atom that cannot be broken down into simpler substances by chemical means. The other options do not explain the observation that the appearance of the sample stayed the same after heating, which is a crucial observation in identifying whether the sample is an element or a compound.
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Identify the type and then write the balanced chemical equation for the reaction described below aluminum oxide breaks down when D heated
According to this equation, two moles of aluminium oxide decompose into three moles of oxygen gas, four moles of aluminium, and two moles of aluminium. Because each element has the equal amount of atoms on both sides of the equation, the reaction is balanced.
What is the equation for the balance of Al h2o to Al2O3 h2?Aluminum oxide and hydrogen gas are created when aluminium metal, or Al, interacts with water. Three moles of water and two moles of aluminium metal, or Al, are combined in this reaction to create one mole of aluminium oxide and three moles of hydrogen gas.
Is the equation h2o2 H2O o2 balanced or unbalanced?This reaction is the result of hydrogen peroxide's spontaneous breakdown into water and oxygen. Because oxygen is a naturally diatomic element, the total number of atoms in each element on both sides of the equation equals one, making the equation balanced.
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how many grams are there in a sample of calcium containing 2.71 x 10^20 particles?
Therefore, there are 0.018 grams of calcium in the sample containing [tex]2.71 * 10^2^0[/tex] particles.
What is Avogadro's number?To calculate the number of grams in a sample of calcium containing 2.71 x 10^20 particles, we need to use the Avogadro's number and the molar mass of calcium.
First, we need to determine the number of moles of calcium in the sample:
Number of particles = [tex]2.71 * 10^2^0[/tex]
Avogadro's number =[tex]6.022 * 10^2^3[/tex]particles/mole
Number of moles = Number of particles / Avogadro's number
[tex]= 2.71 * 10^2^0 / 6.022 * 10^2^3\\= 0.000450 mol[/tex]
The molar mass of calcium is 40.08 g/mol.
Finally, we can calculate the mass of calcium in the sample using the following formula:
Mass (g) = Number of moles x Molar mass
= 0.000450 mol x 40.08 g/mol
= 0.018 g
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if you are walking along a sandy beach and grab a handful of sand, which contained some zircon crystal, could you determine the age of the sand?
Yes, if you are walking along a sandy beach and grab a handful of sand that contains some zircon crystals, you could determine the age of the sand.
Zircon is a mineral that contains a radioactive isotope called zirconium-90. It decays into lead-206 with a half-life of 4.5 billion years.
By analyzing the amount of lead 206 and zirconium 90 in a rock or mineral, scientists can calculate the age of the rock or mineral through a process called radiometric dating.
Radiometric dating is a technique that uses the natural decay rate of unstable isotopes to determine the age of rocks and minerals. Scientists can measure the amount of each isotope in a sample to calculate the age of the sample.
The half-life of a radioactive isotope is the amount of time it takes for half of the parent isotope to decay into the daughter isotope. By knowing the half-life of an isotope, scientists can calculate the age of the sample.
Zircon is a mineral that contains zirconium-90, which decays into lead-206 with a half-life of 4.5 billion years. By measuring the amount of lead-206 and zirconium-90 in a rock or mineral, scientists can calculate the age of the rock or mineral.
This process is called radiometric dating.
Therefore, if you are walking along a sandy beach and grab a handful of sand that contains some zircon crystals, you could determine the age of the sand by analyzing the amount of lead-206 and zirconium-90 in the zircon crystals.
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zeolites have structures that contain cages which are ideal for absorbing materials. true/false
The given statement, "Zeolites have structures that contain cages which are ideal for absorbing materials," is true (T) because zeolites have porous structures with cages that are suitable for adsorbing materials.
Zeolites are a group of porous materials with a crystalline structure consisting of interconnected tetrahedra. This structure results in a network of interconnected channels and cavities, which create cages that are ideal for absorbing and exchanging materials.
The regular size and shape of these cages allow zeolites to selectively adsorb molecules based on their size and shape, making them useful in a wide range of applications such as catalysis, gas separation, and water purification. Furthermore, the high surface area of zeolites enhances their adsorption and exchange capabilities.
Overall, the unique properties of zeolites make them effective materials for various industrial and environmental applications.
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**NEED QUICKLY***
if there are 300,000 servicemen buried on 624 acres wut is the unit rate of average number of servicemen buried for acre
Answer:
To find the unit rate of the average number of servicemen buried per acre, you can divide the total number of servicemen (300,000) by the total number of acres (624).
Here's the calculation:
```
300,000 servicemen / 624 acres = 480.7692307692308
```
So, on average, there are approximately 480.77 servicemen buried per acre.
Identify the type or types of reactions the reaction between zinc and iodine is/are.a. synthesis reactionb. acid base reactionc. double displacement reactiond. single replacement reactione. ombustion reactionf. precipitation reactiong. halogen replacement reactionh. redox reaction
the reaction involves a transfer of electrons from the zinc atoms to the iodine molecules, indicating a redox reaction.
The reaction between zinc and iodine is a single replacement reaction, also known as a redox reaction.
In this reaction, zinc metal (Zn) reacts with iodine (I2) to form zinc iodide (ZnI₂). The zinc atoms lose two electrons to form Zn²⁺ ions, while the iodine molecules gain two electrons to form iodide ions (I-). The reaction can be represented by the following equation:
Zn + I₂ → ZnI₂
Overall, the reaction involves a transfer of electrons from the zinc atoms to the iodine molecules, indicating a redox reaction.
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Give the ion notation for an atom with 6 protons and 2 electrons
An atom with 6 protons and 2 electrons would have a net charge of +4, indicating that it has lost two electrons. This atom is now referred to as a cation, specifically a helium cation (He₂⁺). The ion notation for this atom would be written as He₂⁺.
The notation is a shorthand way of representing the atomic structure of an ion. It includes the chemical symbol of the element followed by the charge of the ion written as a superscript. In this case, the chemical symbol is He, which represents helium. The superscript of 2+ indicates that the helium atom has lost two electrons, leaving it with a net positive charge.
It is important to note that the number of protons in the nucleus of the helium ion remains the same as in a neutral helium atom. However, the number of electrons in the ion has decreased, resulting in a change in its chemical and physical properties. This ion is now more likely to bond with other ions or atoms to regain its lost electrons and become more stable.
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How are particles in air arranged in a Compression?
Answer:
the molecular space between the molecules of air is decreased
a solution contains 0.0430 m ca2 and 0.0970 m ag . if solid na3po4 is added to this mixture, which of the phosphate species would precipitate out of solution first?
The addition of Na₃PO₄, calcium phosphate (Ca₃(PO₄)₂) would precipitate out of solution first.
To determine which phosphate species would precipitate out of solution first, we need to calculate the solubility products (Ksp) of each possible calcium phosphate and silver phosphate species that could form upon the addition of solid Na₃PO₄. The species with the smallest Ksp will be the first to precipitate out of solution.
The possible calcium phosphate species that could form are:
Calcium dihydrogen phosphate (Ca(H₂PO₄)₂), with Ksp = 1.0 x [tex]10^{-7.2}[/tex]
Calcium hydrogen phosphate (CaHPO₄), with Ksp = 2.0 x [tex]10^{-7.2}[/tex]
Calcium phosphate (Ca₃(PO₄)₂), with Ksp = 2.0 x [tex]10^{-29.9}[/tex]
The possible silver phosphate species that could form are:
Silver dihydrogen phosphate (AgH₂PO₄), with Ksp = 1.0 x [tex]10^{-7.2}[/tex]
Silver hydrogen phosphate (Ag₂HPO₄), with Ksp = 1.2 x [tex]10^{-18.6}[/tex]
Silver phosphate (Ag₃PO₄), with Ksp = 1.8 x [tex]10^{-18.7}[/tex]
We can see that the Ksp of calcium phosphate is much smaller than that of any of the silver phosphate species. Therefore, upon the addition of Na₃PO₄, calcium phosphate (Ca₃(PO₄)₂) would precipitate out of solution first.
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7. part f.2. 6 m nh;, a basic solution, cannot be found on the reagent shelf, but 6 m naoh, also a base, is available. what would be observed if the 6 m naoh is substituted for the 6 m nh, in testing the reference solution? explain.
We should take into account what happens when NaOH is added to a reference solution. When a base (NaOH) is added to an acidic solution (reference solution), it will neutralize the acidic solution. So, if 6 M NaOH is used instead of 6 M NH when testing the reference solution, it will also neutralize the acidic solution.
When NaOH is added to the reference solution, it will turn the solution yellow. Because a yellow color would be observed if NaOH is used to test the reference solution, it is not an acceptable substitute for NH3. The presence of NaOH indicates the absence of NH3.The balanced equation for the reaction between NH3 and HCl is:NH3 + HCl → NH4ClThe balanced equation for the reaction between NaOH and HCl is:NaOH + HCl → NaCl + H2OTherefore, since 6 M NaOH is a strong base and 6 M HCl is a strong acid, the reaction will be vigorous, and lots of heat will be generated. Since NH3 is not present, NaOH will react with HCl in the reference solution and neutralize it (yellow color). This indicates the absence of NH3, which is not the goal of the experiment. As a result, NaOH is not an acceptable substitute for NH3 in this situation.
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Which one of the following would form a precipitate with PO3-ions in aqueous solution? A) K+ B) NH4+ C) Ca2+ D) None of these would form a precipitate.
The compound which forms a precipitate with PO3- ions in aqueous solution is Ca2+. The correct option is (C) Ca2+.
When there is a reaction of phosphate (PO43-) with calcium (Ca2+) or magnesium (Mg2+) cations present in the solution, it creates an insoluble compound that will precipitate out of the solution. Aqueous solutions are solutions that are mixed with water. They are usually clear, but they can produce precipitates if certain conditions are met. If a substance is insoluble in water, it will not dissolve in it. As a result, the solution's concentration of that substance will be less than the saturation concentration. If a solution is heated or its pH is altered, the substance's solubility in water can vary. To create a precipitate, two aqueous solutions must combine to produce a solid substance that falls out of solution.
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How was James Oliver's iron plow an improvement over John Deere's steel plow?
James Oliver's iron plow was an improvement over John Deere's steel plow because it was less expensive and lasted longer.
The iron plow was made by casting iron in a mold, which was cheaper and easier than the process used to make steel plows.
Additionally, iron was more durable than steel at the time, meaning it lasted longer and required less maintenance.
This allowed farmers to use the plow for a longer period before having to replace it. While John Deere's steel plow was an improvement over earlier plows, Oliver's iron plow was a significant improvement that revolutionized farming.
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(d) Ionic bonds often have some covalent character. This is influenced by the sizes and
charges of the ions involved. State how these two factors must change, for positive
ions and then for negative ions, to increase the covalent character in an ionic bond.
(i) Positive ions:
15.
16.
(ii) Negative ions:
d
[1]
[1]
(c) Briefly explain why the hydrocarbon ethane, C₂H,, is insoluble in water yet
ethanol, C,H,OH, is readily soluble in water.
[3]
(a) Sketch the electron density distribution in a hydrogen molecule, H₂, in the space
below.
[1]
Answer:
(d) In order to increase the covalent character in an ionic bond, the sizes of the ions must become closer to each other and the charges on the ions must become smaller.
(i) For positive ions, decreasing the size and the charge will increase the covalent character in an ionic bond.
(ii) For negative ions, increasing the size and the charge will increase the covalent character in an ionic bond.
(c) Ethane, C₂H₆, is non-polar, meaning it has no partial charges and is not attracted to the polar water molecules. Ethanol, C₂H₅OH, on the other hand, is polar due to the hydroxyl (-OH) group, which creates partial charges on the molecule that can interact with the water molecules. This allows for the formation of hydrogen bonds between ethanol and water molecules, resulting in ethanol's solubility in water.
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In an experiment, calcium carbonate reacted with different volumes of hydrochloric acid in water. One of the products formed during the experiment was carbon dioxide. The time taken for 0.89 mL of carbon dioxide to form was recorded. A partial record of the experiment is shown.
Based on factors that affect the rates of chemical reactions, which of the following would describe the trend expected in the table?
A. Time increases as the volume of hydrochloric acid decreases
B. Time increases as the volume of hydrochloric acid remains the same
C. Time decreases as the mass of calcium carbonate decreases
D. Time decreases as the mass of calcium carbonate remains the same
Based on the factors that affect the rates of chemical reactions, the trend expected in the table would be:
A. Time decreases as the volume of hydrochloric acid increases.
The rate of a chemical reaction depends on the concentration of the reactants. In this case, the hydrochloric acid is a reactant, and increasing its volume will increase its concentration, leading to a faster reaction rate and shorter time for the formation of carbon dioxide.
Therefore, option A is the correct answer. The mass of calcium carbonate may affect the reaction rate if it affects the surface area or particle size of the reactant, but the information provided in the question is not sufficient to determine such an effect. The volume of hydrochloric acid is a more significant factor in this case.
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In SEC, in what volume would you expect molecules that are much smaller than the fractionation range of the Sephadex SP to elute?A. ViB. VmC. VavD. VrE. Vo
In SEC, molecules that are much smaller than the fractionation range of the Sephadex SP will elute in the void volume, represented by the symbol (option E)Vo.
In SEC (Size Exclusion Chromatography), the separation of molecules is based on their size. Sephadex SP is a matrix with a specific fractionation range that separates molecules based on their size. Molecules that are much smaller than the fractionation range of the Sephadex SP will not interact with the matrix and will not be separated from the void volume (Vo). Therefore, they will elute in the void volume (Vo) which is the volume of the mobile phase that is not retained by the matrix. Hence, the correct option is E. Vo.
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among the following h atom transitions, which would emit a photon of light with the greatest energy? a) n = 5 to n = 3. b) n = 4 to n = 2. c) n = 2 to n = 1. d) n = 5 to n = 4.
The following H atom transitions, that would emit the photon of the light with the greatest energy is n = 2 to n = 1. The correct option is c.
The largest energy is given as :
ΔE = 13.6 ( 1/nf² - 1/ ni²)
a) n = 5 to n = 3
ΔE = 13.6 ( 1/3² - 1/ 5²)
ΔE = 0.97 eV
b) n = 4 to n = 2
ΔE = 13.6 ( 1/2² - 1/ 4²)
ΔE = 2.4 eV
c) n = 2 to n = 1
ΔE = 13.6 ( 1/1² - 1/ 2²)
ΔE = 10.2 eV
d) n = 5 to n = 4
ΔE = 13.6 ( 1/4² - 1/ 5²)
ΔE = 0.7 eV
Thus, the transition would emit the photon of light with the greatest energy is n= 2 to n= 1. The correct option is c.
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Please please please help me this is due in 40 mins!!
The activation energy is 57.53 kJ/mol and the frequency factor is 7.18E+10 s^-1
How to explain the energyIt should be noted that to create a linear plot from the temperature-dependent rate constant data, we need to take the natural logarithm of both sides of the Arrhenius equation. This gives us:
ln(k(T)) = ln(A) - (Ea/RT)
We can rewrite this equation in the form of y = mx + b, where y = ln(k(T)), x = 1/T, m = -Ea/R, and b = ln(A):
y = mx + b
ln(k(T)) = (-Ea/R)(1/T) + ln(A)
Now, we can plot ln(k(T)) versus 1/T using MS Excel and perform linear regression to find the slope and intercept of the line. Here is a table of the given data and the calculated values of ln(k(T)) and 1/T:
T (K) k(T) (s^-1) ln(k(T)) 1/T
200.0 4.35E+06 15.294 0.005
250.0 1.94E+07 16.779 0.004
300.0 5.10E+07 17.738 0.00333
350.0 9.66E+07 18.395 0.00286
400.0 1.72E+08 18.967 0.0025
Using Excel's LINEST function, we can find the slope and intercept of the linear plot:
Slope = -Ea/R = -6.9174E+03 K
Intercept = ln(A) = 25.044
Therefore, the activation energy and frequency factor are:
Ea = -slope x R = 57.53 kJ/mol
A = exp(intercept) = 7.18E+10 s^-1
So the activation energy is 57.53 kJ/mol and the frequency factor is 7.18E+10 s^-1.
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How much heat energy is absorbed
when 7.0 moles of water boils
according to the reaction below?
H₂O(l) → H₂O(g) A = +40.7kJ
amelt = [?] kJ
Energy (kJ)
The quantity of heat absorbed may be calculated by dividing the number of moles of ice by the molar heat of fusion. 3. After heating the water to 0oC, the temperature is increased to 100oC using the equation
H=cpmT
+40.7kJ/7.0 =5.81
and the water specific heat.
How can heat energy become absorbed?Heat is an example of energy. When a substance absorbs heat, the inter-particle linkages between the particles weaken and break, resulting in a change in the state of the substance. Heat does not cause a significant phase shift to raise the temperature.
Because of its low cost, large heat capacity, and excellent transport qualities, water is the most often utilised heat transfer fluid. However, depending on the system pressure, the range of practical temperatures is confined by boiling at high temperatures or freezing below 0 °C.
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Answer: 284.9
Explanation:
acellus verified
10Li + Hd2O5->5Li2O+2HD+Energy
How many moles of lithium are needed to fully react with the 29 gram dosage of hordium oxide
that turns people into zombies (10 points)?
How many grams of lithium would this be (5 points)?
To prevent the element from becoming a gas when heated again, the element is placed in 3
liters of water, forming a solution. What phase of matter is the element now in (5 points)?
What would the molarity of this solution be (10 points)?
To fully react with 29 grams of hordium oxide, 0.648 moles of lithium are needed.This would be equivalent to 6.67 grams of lithium.
Why is it important to balance a chemical equation?Balancing a chemical equation ensures that the number of atoms of each element on the reactant side is equal to the number of atoms of each element on the product side.
This is significant because the rule of conservation of mass mandates that in a chemical reaction, the total masses of the reactants and products must be equal.
What is the significance of the release of energy in a chemical reaction?The release of energy in a chemical reaction indicates that energy is being transferred from the reactants to the surroundings. This can occur in various ways, such as the production of heat, light, or sound.
The release of energy can also indicate that the reaction is exothermic, which means that the products have a lower energy level than the reactants. On the other hand, if the reaction absorbs energy, it is endothermic, and the products have a higher energy level than the reactants.
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Match the following definitions to the most appropriate term: a substance that donates one proton when dissolved in water [ Choose] a substance that donates two protons when dissolved in water [ Choose ] a substance that donates three protons when dissolved in water any ionic compound whose cation comes from a base and whose anion comes from an acid [Choose] the solution in the buret [ Choose] the solution in the flask [Choose]analyte diprotic acid salt triprotic acid monoprotic acid titrant
In acid-base titrations, the titrant is a solution of known concentration that is added to the analyte, which is the solution being analyzed.
The endpoint of the titration is the point at which the reaction between the titrant and analyte is complete, and the amount of titrant required to reach the endpoint is used to calculate the concentration of the analyte. Monoprotic acids donate one proton, diprotic acids donate two protons, and triprotic acids donate three protons when dissolved in water. Salts are formed by the reaction between an acid and a base, resulting in an ionic compound with a cation from the base and an anion from the acid.
Monoprotic acid donates one proton when dissolved in water.
Diprotic acid donates two protons when dissolved in water.
Triprotic acid donates three protons when dissolved in water.
Salt ionic compound whose cation comes from a base and whose anion comes from an acid.
The solution in the buret: titrant
The solution in the flask: analyte
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g which of the following are considerations that should be taken when choosing solvents for recrystallization?the desired compound should be significantly more soluble in one solvent than the other.the solvents should be more basic than the desired compound.the two solvents should have significantly different polarity.
The considerations that should be taken when the choosing solvents for the recrystallization is the desired compound should be the significantly more soluble in one solvent than the other.
The Recrystallization is the process to purify the chemicals in the chemistry. We will mix the compound with impurity then we will purify it again by the using recrystallization method. So. the normal procedure is that to dissolve the substance that is to be purified in the suitable solvent, at the very high temperature, to form the almost saturated solution.
In the recrystallization, the solution is created by the dissolving the solute in the solvent at or the near its boiling point.
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Arrange these ions according to ionic radius. Largest radius Sr2+ Rb+ Se2- Br As3- Smallest radius Arrange these elements according to atomic radius. Largest radius Smallest radius Answer Bank Mg Sr Ca Ba Be Rank the elements by effective nuclear charge, Zeff, for a valence electron. Highest Zeff Lowest Zeff Answer Bank In Sb Rb Sr Sn
Ionic radius: Largest radius > Se2- > Br- > Rb+ > Sr2+ > As3- > Smallest radius
Atomic radius: Largest radius > Ba > Sr > Ca > Mg > Be > Smallest radius
Nuclear charge: Highest Zeff > In > Sn > Sb > Rb > Sr > Lowest Zeff
1. Arrange these ions according to ionic radius.
To arrange these ions, we need to consider the periodic table trends for ionic radii. Ionic radii generally decrease across a period and increase down a group.
Largest radius > Se2- > Br- > Rb+ > Sr2+ > As3- > Smallest radius
2. Arrange these elements according to atomic radius.
We will follow the trend of atomic radii, which typically increase down a group and decrease across a period.
Largest radius > Ba > Sr > Ca > Mg > Be > Smallest radius
3. Rank the elements by effective nuclear charge (Zeff) for a valence electron.
Effective nuclear charge generally increases across a period and decreases down a group.
Highest Zeff > In > Sn > Sb > Rb > Sr > Lowest Zeff
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the half-life of uranium-238 is 4.5 billion years. what is its decay rate? express the rate as a percentage per billion years rounded to four decimal places.
The decay rate is 0.0015 percent per billion years
The decay rate of a radioactive substance refers to the rate at which it undergoes radioactive decay, which is typically measured as the number of radioactive decays per unit time. The decay rate of uranium-238 can be calculated using its half-life, which is the time it takes for half of the original amount of uranium-238 to decay.
The formula for calculating the decay rate of a substance is:
decay rate = (ln 2) / half-life
Substituting the half-life of uranium-238 into the formula, we get:
decay rate = (ln 2) / 4.5 billion years
Using a calculator, we can evaluate the natural logarithm of 2 and divide it by the half-life to get:
decay rate = 0.0000154011 per year
To express this rate as a percentage per billion years, we can multiply the decay rate by 100 and divide it by one billion:
decay rate = (0.0000154011 per year) x (100 / 1 billion years)
decay rate = 0.00154011 percent per billion years
Rounding this value to four decimal places, we get:
decay rate = 0.0015 percent per billion years.
So, The decay rate is 0.0015 percent per billion years
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15. what is the ph of the solution when 0.003 moles of hcl is added to a 30.00 ml buffer solution that contains 0.015 moles of hcooh and 0.015 moles of na hcoo? ka
The pH of the solution when 0.003 moles of HCl is added to a 30.00 ml buffer solution that contains 0.015 moles of HCOOH and 0.015 moles of NaHCOO is 3.02.
What is a buffer solution?A buffer solution is a solution that resists changes in pH when small amounts of acids or bases are added to it. When acids or bases are added to it, the buffer solution can either accept or donate protons, limiting any increase or decrease in pH. Buffer solutions are usually made by mixing a weak acid and its corresponding salt or a weak base and its corresponding salt in a specific proportion to achieve a specific pH.
The equation for the dissociation of formic acid (HCOOH) is:
HCOOH(aq) + H₂O(l) ⇌ H₃O+(aq) + HCOO-(aq)
The Ka expression for formic acid is:
Ka = [H₃O+] [HCOO-]/[HCOOH]
A buffer solution consists of a weak acid (HCOOH) and its corresponding salt (NaHCOO). When the salt dissolves in water, it hydrolyzes to form Na+ and HCOO-. The Na+ ions are spectator ions and do not take part in the equilibrium reaction.
The hydrolysis reaction is:
HCOO-(aq) + H₂O(l) ⇌ H₃O+(aq) + HCOO-(aq)
The equilibrium constant expression for this reaction is:
Kb = [HCOO-][H₃O+]/[HCOOH]
Since Ka × Kb = Kw,
where
Kw is the ion product constant for water,
Kw = [H₃O+][OH-] = 1.0 × 10-14
Ka × Kb = [H₃O+][HCOO-]/[HCOOH][HCOO-][H₃O+] = Ka × [HCOOH][HCOO-][H₃O+] = 1.0 × 10-14[H₃O+] = [HCOO-][HCOOH]/Ka[H₃O+] = 10^-3.52 = 2.51 × 10^-4
pH = -log[H₃O+]
pH = -log(2.51 × 10⁻⁴) = 3.02
Hence, the pH of the solution when 0.003 moles of HCl is added to a 30.00 ml buffer solution that contains 0.015 moles of HCOOH and 0.015 moles of NaHCOO is 3.02.
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Alcohol and other depressant drugs, the activity of a person central nervous system
Alcohol and other depressant drugs, slows down your central nervous system the activity of a person central nervous system.
How can depressants like alcohol and others affect the central nervous system?Alcohol is a Central Nervous System Depressant, which means that it reduces neural activity and brain activity. By boosting the actions of the neurotransmitter GABA, alcohol achieves this.
Because it slows down your central nervous system, alcohol is referred to as a psychotropic depressant. When you consume alcohol, a complex mechanism takes place in your brain that affects the neurons' capacity to conduct impulses, inhibiting them.
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cars run on gasoline, where octane (c8h18) is the principle component. this combustion reaction is responsible for generating enough energy to move a vehicle, or do other work. how much co2 and h2o (in grams) are produced in the combustion of 0.87 gallons of octane? (density of octane
The combustion of 0.87 gallons of octane produces approximately 6.98 kg of CO₂ and 3.21 kg of H₂O.
To calculate the amount of CO₂ and H2O produced in the combustion of octane, we need to first convert the volume of octane from gallons to moles using its density and molar mass.
The density of octane is around 0.703 g/mL and its molar mass is 114.23 g/mol. One gallon is approximately 3.785 liters.
So, the amount of moles of octane in 0.87 gallons is:
moles of octane = (0.87 gallons) x (3.785 L/gallon) x (0.703 g/mL) / (114.23 g/mol) = 19.8 moles
The balanced chemical equation for the combustion of octane is:
2 C₈H₁₈ + 25 O₂ → 16 CO₂ + 18 H₂O
From this equation, we see that 2 moles of octane reacts with 25 moles of oxygen to produce 16 moles of CO₂ and 18 moles of H₂O.
Using stoichiometry, we can calculate the amount of CO₂ and H₂O produced from 19.8 moles of octane:
moles of CO₂ produced = 16/2 x 19.8 moles = 158.4 molesmoles of H₂O produced = 18/2 x 19.8 moles = 178.2 molesTo convert moles to grams, we can use the molar mass of each compound:
mass of CO₂ produced = 158.4 moles x 44.01 g/mol = 6,979 g or 6.98 kg (rounded to 2 decimal places)mass of H₂O produced = 178.2 moles x 18.02 g/mol = 3,209 g or 3.21 kg (rounded to 2 decimal places)Therefore, the combustion of 0.87 gallons of octane produces approximately 6.98 kg of CO₂ and 3.21 kg of H₂O.
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by definition, exergonic reactions (reactions with a negative dg) occur spontaneously. what keeps the molecules of an exergonic reaction from breaking apart and cell chemistry from racing out of control?
By definition, exergonic reactions (reactions with a negative dg) occur spontaneously. To prevent the molecules of an exergonic reaction from breaking apart and cell chemistry from racing out of control, enzymes keep them in check.
An exergonic reaction is one in which the free energy of the products is lower than the free energy of the reactants. Exergonic reactions are often referred to as spontaneous reactions because they are spontaneous and do not require energy to proceed.Examples of exergonic reactionsA reaction that breaks a large molecule into two smaller ones, releasing energy in the process, is an example of an exergonic reaction. The breakdown of glucose into carbon dioxide and water is one such reaction.
The breakdown of ATP to ADP is another example. Enzymes, which are catalysts that speed up chemical reactions, keep the molecules of an exergonic reaction in check, preventing them from breaking apart and cell chemistry from going out of control. Without enzymes, many exergonic reactions would take place too slowly to sustain life, while others would go too quickly, causing cell damage or even death.
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why is it necessary to heat under reflux for this reaction, as opposed to simply boiling the mixture in an open flask?
As compared to simply boiling the mixture in an open flask, it is necessary to heat under reflux for this reaction because: During a reflux, the volatile solvent that evaporates from the reaction mixture condenses back into the reaction flask, allowing the reaction mixture to stay at a constant temperature.
During the reaction, a side product, water, is formed. Boiling in an open flask would cause the water to evaporate along with the solvent, leading to a lower yield of the desired product. In comparison, refluxing allows the water to condense and remain in the reaction mixture, ensuring that the reaction proceeds as intended and that the yield of the desired product is high. Aside from the aforementioned reasons, it is necessary to heat under reflux for this reaction since refluxing allows the reaction to proceed to completion. When the solvent vaporizes, the vapor carries with it the product, which condenses back into the flask due to the condenser's cooling effect. This allows the reaction to proceed to completion, resulting in a higher yield of the desired product. This technique also prevents the product from overheating, preventing its decomposition or degradation.
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