Exactly 1.5 g of a fuel burns under conditions of constant pressure and then again under conditions of constant volume. In measurement A the reaction produces 25.9 kJ of heat, and in measurement B the reaction produces 23.3 kJ of heat. Which measurement (A or B) corresponds to conditions of constant pressure? Explain.

When 1.03 g of biphenyl (C12H10) undergoes combustion in a bomb calorimeter, the temperature rises from 24.2 °C to 2931.4 °C. Find ΔErxn for the combustion of biphenyl in kJ>mol biphenyl. The heat capacity of the bomb calorimeter, determined in a separate experiment, is 5.86 kJ/°C.

Zinc metal reacts with hydrochloric acid according to the balanced equation: Zn(s) + 2 HCl(aq) → ZnCl₂(aq) + H₂(g) When 0.103 g of Zn(s) is combined with enough HCl to make 50.0 mL of solution in a coffee-cup calorimeter, all of the zinc reacts, raising the temperature of the solution from 22.5 °C to 23.7 °C. Find ΔH_rxn for this reaction as written. (Use 1.0 g/mL for the density of the solution and 4.18 J/g•°C as the specific heat capacity.)

Instant cold packs used to ice athletic injuries on the field contain ammonium nitrate and water separated by a thin plastic divider. When the divider is broken, the ammonium nitrate dissolves according to the endothermic reaction: NH₄NO₃(s) → NH₄⁺(aq) + NO₃^– (aq) In order to measure the enthalpy change for this reaction, 1.25 g of NH₄NO₃ is dissolved in enough water to make 25.0 mL of solution. The initial temperature is 25.8 °C and the final temperature (after the solid dissolves) is 21.9 °C. Calculate the change in enthalpy for the reaction in kJ. (Use 1.0 g/mL as the density of the solution and 4.18 J/g•°C as the specific heat capacity.)

For each generic reaction, determine the value of ΔH₂ in terms of ΔH₁.

a. A + B → 2 C ΔH₁

2 C→ A + B ΔH₂ = ?

For each generic reaction, determine the value of ΔH₂ in terms of ΔH₁.

b. A + 1/2 B → C ΔH₁

2 A + B → 2 C ΔH₂ = ?

For each generic reaction, determine the value of ΔH₂ in terms of ΔH₁.

c. A → B + 2 C ΔH₁

1/2 B + C → 1/2 A ΔH₂ = ?

Consider the generic reaction:

A + 2 B → C + 3 D ΔH = 155 kJ

Determine the value of ΔH for each related reaction.

a. 3 A + 6 B → 3 C + 9 D

b. C + 3 D → A + 2 B

c. 1/2 C + 3/2 D → 1/2 A + B

Calculate ΔH_rxn for the reaction:

Fe₂O₃(s) + 3 CO(g) → 2 Fe(s) + 3 CO₂(g)

Use the following reactions and given ΔH's:

2 Fe(s) + 3/2 O₂(g) → Fe₂O₃(s) ΔH = –824.2 kJ

CO(g) + 1/2 O₂(g) → CO₂(g) ΔH = –282.7 kJ

Calculate ΔHrxn for the reaction:

5 C(s) + 6 H₂(g) → C₅H₁₂(l)

Use the following reactions and given ΔH's:

C₅H₁₂(l) + 8 O₂(g) → 5 CO₂(g) + 6 H₂O(g) ΔH = –3244.8 kJ

C(s) + O₂(g) → CO₂(g) ΔH = –393.5 kJ

2 H₂(g) + O₂(g) → 2 H₂O(g) ΔH = –483.5 kJ

Write an equation for the formation of each compound from its elements in their standard states, and find ΔH°_rxn for each in Appendix IIB. b. MgCO₃(s)

Write an equation for the formation of each compound from its elements in their standard states, and find ΔH°_rxn for each in Appendix IIB. d. CH₃OH(l)

Hydrazine (N₂H₄) is a fuel used by some spacecraft. It is normally oxidized by N₂O₄ according to the equation: N₂H₄ (l) + N₂O₄ (g) → 2 N₂O (g) + 2 H₂O (g) Calculate ΔH°_rxn for this reaction using standard enthalpies of formation.

Pentane (C₅H₁₂) is a component of gasoline that burns according to the following balanced equation: C₅H₁₂(l) + 8 O₂(g) → 5 CO₂(g) + 6 H₂O(g) Calculate ΔH°_rxn for this reaction using standard enthalpies of formation. (The standard enthalpy of formation of liquid pentane is –146.8 kJ/mol.)

Use standard enthalpies of formation to calculate ΔH°_rxn for each reaction. a. C₂H₄(g) + H₂(g) → C₂H₆(g)

Use standard enthalpies of formation to calculate ΔH°_rxn for each reaction. c. 3 NO₂(g) + H₂O(l) → 2 HNO₃(aq) + NO(g)

Use standard enthalpies of formation to calculate ΔH°_rxn for each reaction. d. Cr₂O₃(s) + 3 CO(g) → 2 Cr(s) + 3 CO₂(g)

Use standard enthalpies of formation to calculate ΔH°_rxn for each reaction. a. 2 H₂S(g) + 3 O₂(g) → 2 H₂O(l) + 2 SO₂(g)

Use standard enthalpies of formation to calculate ΔH°_rxn for each reaction. b. SO₂(g) + 1/2 O₂(g) → SO₃(g)

Use standard enthalpies of formation to calculate ΔH°_rxn for each reaction. d. N₂O₄(g) + 4 H₂(g) → N₂(g) + 4 H₂O(g)

During photosynthesis, plants use energy from sunlight to form glucose (C₆H₁₂O₆) and oxygen from carbon dioxide and water. Write a balanced equation for photosynthesis.

Ethanol (C₂H₅OH) can be made from the fermentation of crops and has been used as a fuel additive to gasoline. Write a balanced equation for the combustion of ethanol and calculate ΔH°_rxn.

Top fuel dragsters and funny cars burn nitromethane as fuel according to the balanced combustion equation: 2 CH₃NO₂(l) + 3/2O₂(g) → 2 CO₂(g) + 3 H₂O(l) + N₂(g) ΔH°_rxn = –1418 kJ The enthalpy of combustion for nitromethane is –709.2 kJ/mol. Calculate the standard enthalpy of formation (ΔH°_f ) for nitromethane.

The explosive nitroglycerin (C₃H₅N₃O₉) decomposes rapidly upon ignition or sudden impact according to the balanced equation: 4 C₃H₅N₃O₉(l) → 12 CO₂(g) + 10 H₂O(g) + 6 N₂(g) + O₂(g) ΔH°_rxn = –5678 kJ Calculate the standard enthalpy of formation (ΔH°_f ) for nitroglycerin.

Determine the mass of CO₂ produced by burning enough of each fuel to produce 1.00×10² kJ of heat. a. CH₄(g) + 2 O₂(g) → CO₂(g) + 2 H₂O(g) ΔH°_rxn = –802.3 kJ

In a sunny location, sunlight has a power density of about 1 kW/m². Photovoltaic solar cells can convert this power into electricity with 15% efficiency. If a typical home uses 385 kWh of electricity per month, how many square meters of solar cells are required to meet its energy requirements? Assume that electricity can be generated from the sunlight for 8 hours per day.