When 3.93 grams of lactic acid, CHoOs(s), are burned in a bomb
calorimeter that has a total heat capacity of 10.80 kJ-K-1, the
temperature of the calorimeter increases by 5.43 K. Assume AHrxn
=
AErxn. Given that AH°f of H¿O(I) = -285.8 kJ-mol-1 and AH°f of CO:(g)
= -393.5 kJ• mol-1, calculate the AH°f of lactic acid.
Answers
The heat released in the combustion of lactic acid is absorbed by the
calorimeter and in the decomposition of the lactic acid.
ΔH°f of lactic acid is approximately -716.2 kJ
Reasons:
Known parameters are;
Mass of the lactic acid = 3.93 grams
Heat capacity of the bomb calorimeter = 10.80 kJ·K⁻¹
Change in temperature of the calorimeter, ΔT = 5.34 K
ΔHrxn = ΔErxn
ΔH°f of H₂O(l) = -285.8 kJ·mol⁻¹
ΔH°f of CO₂(g) = -393.5 kJ·mol⁻¹
The chemical equation for the reaction is presented as follows;
C₃H₆O₃ + 2O₂ → 3CO₂ + 3H₂OThe heat of the reaction = 10.80 kJ·K⁻¹ × 5.34 K = 57.672 kJ
Molar mass of C₃H₆O₃ = 90.07 g/mol
Number of moles of C₃H₆O₃ = [tex]\dfrac{3.93 \, g}{90.07 \, g/mol}[/tex] = 0.043633 moles
Number of moles of CO₂ produced = 3 × 0.043633 moles = 0.130899 moles
Heat produced = 0.130899 mole × -285.8 kJ·mol⁻¹ = -37.4109342 kJ
Moles of H₂O produced = 0.130899 moles
Heat produced = 0.130899 mole × -393.5 ≈ -51.51 kJ
Therefore, we have;
Heat absorbed by the lactic acid = ΔH°f of H₂O + ΔH°f of CO₂ + Heat absorbed by the calorimeter
Which gives;
Heat absorbed by lactic acid = -37.4109342 kJ - 51.51 kJ + 57.672 kJ ≈ -31.249 kJ
The heat absorbed by the lactic acid ≈ -31.249 kJ
[tex]\Delta H^{\circ}f \ of \ C_3H_6O_3 = \dfrac{-31.249}{0.043633} \approx -716.2[/tex]
ΔH°f of C₃H₆O₃ ≈ -716.2 kJ
Heat of formation of lactic acid ≈ -716.2 kJ.
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Related Questions
Can you give a definition of what Sodium Hydroxide
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Answer:
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations Na⁺ and hydroxide anions OH⁻
Explanation:
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According to the law of conservation of matter, which statement about chemical reactions is true? A. Atoms cannot be created or destroyed by chemical reactions. B. Atoms are created by some reactions and destroyed by others. C. Energy is created as atoms are destroyed in chemical reactions. D. Every atom destroyed in a chemical reaction must be replaced.
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what happens to a circuits resistance (R), voltage (V), and current (I) when you increase the diameter of the wire in the circuit?
a. R increases, V is constant, I increases
b. R decreases, V is constant, I increases
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d. R increases, V decreases, I decreases
Answers
Answer:
b. R decreases, V is constant, I increases
Explanation:
when we increase the diameter of wire increases ,resistance decreases and current increases.Therefore, the option is b.
Resistance is an electrical quantity which opposes the electric current in the circuit. Resistance is directly proportional to the length of the wire and inversely proportional to the diameter of the wire. If length of wire increases resistance will increases and if the diameter of the wire increase resistance will decreases.
R = ρ L/A
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L is the length of the wire
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Voltage is the potential difference between two terminals of voltage source. Current is the flow of electrons in the circuit. Voltage is the product of current and resistance.
V=IR
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. The atomic number of a newly discovered element is found to be 128, and its mass number is 279.
How many protons, neutrons, and electrons are found in an ion of this element bearing a charge of
5−?
Answers
A-128
P-128
E-128
M-279
A-128
N-151
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A compound's properties are different than the properties of the elements that make it up.
A)True
B)False
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True
All matter is made up of atoms.
im guessing it probably true
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What is the lead concentration of a saturated solution of lead(II) sulfate containing 0.020 M Na2SO4? Ksp for PbSO4 = 6.3x10-7.
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Answer:
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Explanation:
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Examine the false statement. When pressure is added to a reaction at chemical equilibrium, the reaction responds by increasing the amount of pressure it exerts on its surroundings. Select the rewording that makes the statement true.
A. When pressure is added to a reaction at chemical equilibrium, the reaction responds by increasing the rate of reaction, which will decrease the number of particles and offset the pressure.
B. When pressure is removed from a reaction at chemical equilibrium, the reaction responds by decreasing the amount of pressure it exerts on its surroundings.
C. When pressure is removed from a reaction at chemical equilibrium, the reaction responds by increasing the rate of reaction, which will decrease the number of particles and increase the pressure.
D. When pressure is removed from a reaction at chemical equilibrium, the reaction responds by decreasing the amount of pressure it releases to its surroundings.
E. When pressure is added to a reaction at chemical equilibrium, the reaction responds by decreasing the amount of pressure it absorbs from its surroundings.
IT'S NOT C OR E
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Answer:
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The electronic transition in a hydrogen atom from n = 6 to n = 3 emits electromagnetic radiation having a higher frequency than a transition
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Which has more calories: table sugar or aspartame?
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Answer:
Aspartame produces 4 kilocalories of energy per gram when metabolized, sucrose (table sugar) produces 3.9 kilocalories. However, aspartame is approximately 200 times sweeter than sucrose, so it is consumed in much smaller doses.
Explanation:
Answer is Aspartame.
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a. gas atoms are smaller than liquid atoms.
b. gas atoms are larger than liquid atoms
c. atoms in a gas are farther apart than atoms in a liquid.
d. atoms in a gas are closer together than atoms in a liquid
Answers
Answer:
c
Explanation:
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When doing medical research with human subjects, which four limitations are unavoidable?
Answers
Answer:
Answer
The limitations are-
1. Privacy of the individuals involved in the research process.
2. Physical and psychological risks should be minimized
3. The subjects should be chosen equitably
4. Only reasonable exposure to risks is admissible.
Explanation
The privacy of the individuals involved in the research must be taken into consideration. This will ensure safety of patient data and information. The risk of physical and physiological well being of the person must be taken into consideration in such a research. In addition to that, the subject must be made to understand every procedure and the risks involved before testing. Moreover, only minimal exposure to risks is allowed and must have been previously tested in animals to avoid deaths.
Consider:
2Al (s) + 3Cl2 (g) ----> 2AlCl3 (s) ΔH=-1390.81 kJ
Which of the following correctly describes he magnitude and direction of the enthalpy change when 10.0g of AlCl3 forms?
a. 104.4 kJ, exothermic
b. 52.2 kJ, exothermic
c. 26.1 kJ, exothermic
d. 52.2 kJ, endothermic
e. 26.1 kJ, endothermic
Answers
Answer:
The answer is B.
Explanation:
1 mole of AlCl3 = 27 + 3*35.5 grams = 133.5 grams
1 mole / 133.5 = x / 10 Cross multiply
133.5 x = 1 * 10
x = 10 / 133.5
x = 0.0749 moles
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So now you get the answer between AB and C by setting up a ratio.
2/0.0749 = -1390.81 / x Cross multiply
2x = 0.0749 * -1390.81
2x =- 104.18 Divide both sides by 2
2x//2 = -104.18 / 2
x = -52.09
B
Calculate the number of days after the explosion for a sample of iodine-131 to go from 100%
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Answers
It will take 56 days to go from 100% iodine-131 to less than 1% iodine-131.
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After 56 days, we will have 0.78125% of iodine-131
After 56 days, the percentage of iodine-131 drops to less than 1%.
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Answers
Your answer→ The lighter side absorbs less of the incident light, reflecting some of the energy. Darker materials also emit radiation more readily than light-colored materials, so they cool faster.
To solve this we must be knowing each and every concept related to radiation. Therefore, dark surfaces absorb radiation better than light surfaces as dark surfaces absorbs light of all wavelengths.
What is radiation?According to the energy of the emitted particles, radiation is frequently classified as being either ionizing or non-ionizing. More than 10 eV is often carried by ionizing radiation, which is sufficient to ionize atoms as well as molecules and rupture chemical bonds.
The word refers to radiation having an energy level high enough to ionize atoms, or to remove electrons from atoms to produce ions. Whenever an electron is removed from an atom's electron shell, or, as we may say, when it is "tried to knock out," the action of ionization takes place. Dark surfaces absorb radiation better than light surfaces as dark surfaces absorbs light of all wavelengths.
Therefore, dark surfaces absorb radiation better than light surfaces as dark surfaces absorbs light of all wavelengths.
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Câu 15: Nguyên tử X nặng gấp 2 lần nguyên tử cacbon. Nguyên tử X đó có nguyên tử khối và
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A. 24_Mg. B. 16_O C. 56_Fe D. 32_S
Answers
Answer:
A
Explanation:
A 3.90 L sealed vessel under vacuum is filled with 6.40 g of fluorine gas. What is the pressure (in kPa) of the vessel at 25.0 ⁰C ?
Answers
From the ideal gas law, the pressure of the gas is 106 kPa.
First we must obtain the number of moles of the gas;
Number of moles = mass/molar mass
Molar mass of fluorine gas = 38 g/mol
Number of moles of F2 = 6.40 g/38 g/mol = 0.168 moles
Using the ideal gas equation;
PV = nRT
P = ?
V = 3.90 L
n = 0.168 moles
T = 25.0 ⁰C + 273 = 296 K
R = 8.314 kPa L K-1 mol-1
Substituting values;
P = nRT/V
P = 0.168 moles × 8.314 kPa L K-1 mol-1 × 296 K/3.90 L
P = 106 kPa
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The pressure of the vessel at a temperature of 25 °C is 106.73 KPa
We'll begin by calculating the number of mole of fluorine gas. This can be obtained as follow:
Mass of F₂ = 6.40 g
Molar mass of F₂ = 19 × 2 = 38 g/mol
Mole of F₂ =?Mole = mass / molar mass
Mole of F₂ = 6.40 / 38
Mole of F₂ = 0.168 moleFinally, we shall determine the pressure. This can be obtained as follow:
Volume (V) = 3.90 L
Temperature (T) = 25.0 °C = 25 + 273 = 298 K
Mole of F₂ (n) = 0.168 mole
Gas constant (R) = 8.314 L.KPa/Kmol
Pressure (P) =?PV = nRT
P × 3.9 = 0.168 × 8.314 × 298
P × 3.9 = 416.232096
Divide both side by 3.90
P = 416.232096 / 3.90
P = 106.73 KPaTherefore, the pressure of the vessel is 106.73 KPa
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can someone help me please ... god will bless u if u help...it is very urgent... i only have 1hr to answer this question
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Answer:
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(iii) Explain why magnesium chloride has a high melting point.
Answers
Answer:
magnesium chlorides are solids with high melting and boiling points because of the large amount of heat which is needed to break the strong ionic attractions.
Explanation:
These magnesium ions have more than one charge (2+). These highly charged ions will attract other ions more strongly than ions with one charge, therefore more energy will be needed to overcome the electrostatic forces of attraction and so the melting points will be higher.
Which statement describes the bonds in nitrate (NO3-)?
A) Nitrogen and oxygen have an electronegativity difference of 0.5, so the bond is polar covalent, with oxygen pulling the electrons toward it.
B) Nitrogen and oxygen have an electronegativity difference of 0.5, so the bond is nonpolar covalent.
C) Nitrogen and oxygen have an electronegativity difference of 0.5, so the bond is ionic.
D) Nitrogen and oxygen have an electronegativity difference of 0.5, so the bond is polar covalent, with nitrogen pulling the electrons toward it.
Answers
The bond in NO3- ion is polar covalent and oxygen pulls the electrons.
A polar covalent bond is formed when there is a significant difference in electronegativity between covalently bonded atoms.
Such bonds are said to be polar covalent with the electron density tilted towards one of the bonding atoms.
In NO3-, Nitrogen and oxygen have an electronegativity difference of 0.5, so the bond is polar covalent, with oxygen pulling the electrons toward it.
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The answer is A, Nitrogen and oxygen have an electronegativity of 0.5, so the bond is polar covalent, with oxygen pulling the electrons toward it.
Electronegativity is defined as, a value that describes the relative strength with which an atom of an element attracts electrons to itself in a chemical bond. Moreover, electronegativity can be used to define a bond.
A electronegativity of 0.5-1.7 is determined to be a polar covalent bond, thus the bonds in nitrate is polar covalent.
We know that electronegativity increases on the periodic table across a period, but decreases down a group. Thus, oxygen has a greater electronegativity than nitrogen.
The change in internal energy for the combustion of cyclohexanol (C6H12O) is -890.7 Kcal per mole. A .708 g sample of cyclohexanol undergoes complete combustion in a bomb calorimeter that has a heat capacity of 2.70 Kcal per degree C. What is the final temperature of the water in the calorimeter if the initial water temperature is 27C?
Answers
The final temperature in the calorimeter, with a heat capacity of 2.70 kcal/°C, internal energy for the combustion of cyclohexanol (C₆H₁₂O) of -890.7 kcal/mol and initial temperature of 27°C, is 29.33 °C.
We can find the final temperature of the water in the calorimeter with the following equation:
[tex]\Delta E = -C\Delta T = -C(T_{f} - T_{i})[/tex] (1)
Where:
ΔE: is the change in internal energy for the combustion of C₆H₁₂O = -890.7 Kcal/mol
C: is the heat capacity of the calorimeter = 2.70 Kcal/°C
[tex]T_{f}[/tex]: is the final temperature =?
[tex]T_{i}[/tex]: is the initial temperature = 27 °C
By solving equation (1) for [tex]T_{f}[/tex], we have:
[tex] T_{f} = -\frac{\Delta E}{C} + T_{i} [/tex]
[tex]T_{f} = -\frac{-890.7 \frac{kcal}{mol\: C_{6}H_{12}O}*\frac{1 mol \: C_{6}H_{12}O}{100.158 g \: C_{6}H_{12}O}*0.708 g \: C_{6}H_{12}O}{2.70 kcal/^{\circ}C} + 27 ^{\circ}C = 29.33 ^{\circ}C[/tex]
Therefore, the final temperature of the water is 29.33 °C.
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A force of 500 N acts over an area of 10 m2. Use the
formula to calculate the pressure.
Answers
Answer:
50Pa
Explanation:
pressure= force/area
= 500N/10m2
= 50Pa
If you have 4.01 g of H2, how many grams of NH3 can be produced?
Answers
Answer:
136.5886g of NH3
Explanation:
N2 + 3H2 = 2NH3
The mass of the N2 = 4.01
3H2 has a 2/1 ratio
This means the mass of 3H2 is twice as much as N2.
NH3= 2*N2 = 2*4.01 = 8.02 of NH3
Then, by multiplying the mass by MX (17.031)
8.02*17.031=136.5886g can be produced. Round it if needed.
what is the difference between exergonic and exothermic reactions?
Answers
Answer:
An exergonic reaction is a type of chemical reaction that releases free energy to the surroundings. The final state of this reaction is less than its initial state. ... “Exothermic” literally means “outside heating” while “exergonic” literally means “outside work.”
Explanation:
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How many mL of 1.76 M sodium hydroxide solution (strong base) must be added to 0.75
Macetic acid to make 683 mLa pH 49 buffer? (pka of acetic acid is 4.76)
Answers
Answer: Special care is required to prepare a solution of sodium hydroxide or NaOH in water because considerable heat is liberated by the exothermic reaction. The solution may splatter or boil. Here is how to make a sodium hydroxide solution safely, along with recipes for several common concentrations of NaOH solution.
Explanation:
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What mineral is composed of sodium chloride (NaCl)?
Answers
Answer:
Salt
Explanation:
The mineral form halite , or rock salt is sometimes called common salt