A silver block, initially at 58.5 °C, is submerged into 100.0 g of water at 24.8 °C, in an insulated container. The final temperature of the mixture upon reaching thermal equilibrium is 26.2 °C. What is the mass of the silver block?

A 32.5-g iron rod, initially at 22.7 °C, is submerged into an unknown mass of water at 63.2 °C, in an insulated container. The final temperature of the mixture upon reaching thermal equilibrium is 59.5 °C. What is the mass of the water?

A 31.1-g wafer of pure gold, initially at 69.3 °C, is submerged into 64.2 g of water at 27.8 °C in an insulated container. What is the final temperature of both substances at thermal equilibrium?

A 2.85-g lead weight, initially at 10.3 °C, is submerged in 7.55 g of water at 52.3 °C in an insulated container. What is the final temperature of both substances at thermal equilibrium?

Two substances, A and B, initially at different temperatures, come into contact and reach thermal equilibrium. The mass of substance A is 6.15 g and its initial temperature is 20.5 °C. The mass of substance B is 25.2 g and its initial temperature is 52.7 °C. The final temperature of both substances at thermal equilibrium is 46.7 °C. If the specific heat capacity of substance B is 1.17 J/g•°C, what is the specific heat capacity of substance A?

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 0.514 g of biphenyl (C₁₂H₁₀) undergoes combustion in a bomb calorimeter, the temperature rises from 25.8 °C to 29.4 °C. Find ΔE_rxn 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.)

Determine whether each process is exothermic or endothermic and indicate the sign of ΔH. a. natural gas burning on a stove b. isopropyl alcohol evaporating from skin c. water condensing from steam Indicate the sign of ΔH for the following processes.

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:

CaO(s) + CO₂(g) → CaCO₃(s)

Use the following reactions and given ΔH's:

Ca(s) + CO₂(g) + 1/2 O2(g) → CaCO₃(s) ΔH = –812.8 kJ

2 Ca(s) + O₂(g) → 2 CaO(s) ΔH = –1269.8 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

Calculate ΔHrxn for the reaction:

CH₄(g) + 4 Cl₂(g) → CCl₄(g) + 4 HCl(g)

Use the following reactions and given ΔH's:

C(s) + 2 H₂(g) → CH₄(g) ΔH = –74.6 kJ

C(s) + 2 Cl₂(g) → CCl₄( g) ΔH = –95.7 kJ

H₂(g) + Cl₂(g) → 2 HCl( g) ΔH = –92.3 kJ

Write an equation for the formation of each compound from its elements in their standard states, and find ΔH °f for each in Appendix IIB. a. NH₃(g)

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. a. NO₂(g)

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)