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11 Dec 2019

In a reaction of a potential new fuel, it is found that when 2.29 moles of the fuel combusts, 1,779 kJ of energy is released. What is the delta Hrxn for the combustion of the fuel in units of kJ/mol.

A reaction in aqueous solution is run in a calorimeter and it is found that the the solution gains 96 kJ of heat and the calorimeter gains 9 kJ of heat. What is the heat gained or lost by the reaction (qrxn) in kJ?

The ? Hrxn for the reaction A + B ? C is 17 kJ.

What is ?Hrxn for the reaction 4A + 4B ? 4C in kJ?

The ? Hrxn for the reaction A + B ? C is 17 kJ.

What is ?Hrxn for the reaction 4C -? 4A + 4B in kJ?

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Beverley Smith
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13 Dec 2019

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Related questions

7. Write out a balanced combustion reaction for methane (CH4). Given that ΔHrxn for this reaction is -890 kJ/mol, what is ΔHrxn for the reaction of 0.5 mol CO2 with sufficient water, producing methane and oxygen?

8. Given that the specific heat of water is 4.184 J/gK, how much heat (in Joules) does it take to raise the temperature of 500.0 mL of water by 50.0∞C (density of water is 1g/mL)?

9. 25.0 mL of 2.00M HCl and 25.0 mL of 1.00M NaOH are mixed in a coffee cup calorimeter. The temperature increases from 25.6∞C to 28.2∞C. What is the enthalpy of the reaction?

10. If a sample of food is burned in a bomb calorimeter with a heat capacity of 15.2kcal/∞C and the temperature increases from 28.3∞C to 35.5∞C, what is the caloric content of the food (report answer in FOOD CALORIES).

11. Calculate the ΔHrxn for 2 S(s) + 3 O2(g) → 2 SO3(g), given the following:

S(s) + O2(g) → SO2(g), ΔHrxn = -296.8 kJ/mol

2 SO3(g) → 2 SO2(g) + O2(g), ΔHrxn = +198.4 kJ/mol

12. Write out a balanced reaction for formation of ethanol (C2H5OH(l)) from elements, assuming the most stable elemental form of carbon is C(graphite).

1. Complete and balance the following chemical reaction: NH4NO3(s) + H2O(l) --> ?

Given

2. Volume of DI water used 50 mL

3. Mass of DI water 50 g

4. Initial temperature of water, Ti 22.5°C

5. Mass of NH4NO3 3.0 g

6. Moles of NH4NO3 ________0.0375__________mol

7. Final temperature of water, Tf 18.9°C

8. change in temperature of the water (?T) -3.6 °C

9. calculate the heat associate with water, qH2O ___ ___-752.4_____________ J

m*c* deltaT = (50g)(4.184 J/g*k)(-3.6) = -752.4

10. the heat either released or absorbed by the reaction (?Hrxn) ________+752.4____________ J

Question: [Please notice the units]

11. Calculate the change in enthalpy (?Hrxn) for this reaction. _____________ kJ ??

12. Calculate the heat of reaction in kJ per mole of NH4NO3 ______________ kJ/mol ??

13. If the heat capacity of the calorimeter was 25 J/oC, what would the new change in enthalpy (?Hrxn) for this reaction be? (Use equation 7 to recalculate the value from #10) ____________________ kJ/mol ?? [Equation 7: - q(rxn) = q(soln) + q(calorimeter)

14. Is this an exo- or endothermic reaction? Explain the reasoning behind your choice. ??

15. Calculate the change in enthalpy for the reaction (?Hrxn) per mole using equation 8 and Table 2. NH4NO3 (s) --> NH4NO3 (aq)

__________________kJ/mol ?? [Equation 8: ?Hrxn = sum{ n?Hf (products) - sum{ n?Hf (reactants)

16. What is the percent error between your value and the value calculated from 13? What are some possible sources of error in the experiment?

__________________% error

A bomb calorimeter was calibrated by burning 1.031 g of benzoic acid (C6H5COOH, M = 122.13g/mol) in excess oxygen. The temperature inside the calorimeter rose from 23.2°C to 36.7°C.

a. What is the heat capacity of the bomb calorimeter, in units of kJ/°C? ΔrU = -3230 kJ/(1 mol benzoic acid)

b. Nitromethane, (CH3NO2 M = 61.04 g/mol), commonly known as “nitro”, is the fuel used in racing cars. Write the formation reaction for liquid nitromethane.

c. A sample of nitromethane was burned in the bomb calorimeter calibrated above. The following energy value was determined for the balanced reaction:

4CH3NO2(l) + 3 O2(g) → 4 CO2(g) + 6 H2O(l) + 2 N2(g) ΔrU= -3740 kJ/mol

Calculate ΔHf for nitromethane, in units of kJ/mol.

• Assume that ΔrH= ΔrU within the accuracy of this experiment.

•ΔfH°(gaseous CO2) = - 393.52 kJ/mol ΔfH°(liquid H2O) = - 285.83 kJ/mol.

d. It is assumed above that ΔrH= ΔrU for the combustion of nitromethane.

• Estimate how much work is done, in units of kJ/mol, for the combustion reaction as written in part c at 298 K.

•Is work done by the system, the surroundings, or neither?

•Justify whether the assumption is a valid one.

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