Back
Problem 2
A room-temperature balloon filled with air is placed in the freezer and the balloon contracts. What is the sign of q and w for the air inside the balloon? (LO 9.4) (a) q = +, w = - (b) q = +, w = + (c) q = -, w = - (d) q = -, w = +Problem 4
For which of the following reactions are ΔE and ΔH equal? (a) CO2(g) + H2O(l) → H2CO (b) 2 NaHCO3 (s) → Na2CO3(s) + H2O(g) + CO2(g) (c) 2 H2(g) + O2(g) → 2 H2O(g) (d) CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g)Problem 6a
Several processes are given in the table and labeled as endo- thermic or exothermic and given a sign for ∆H°. Which process is labeled with the correct sign of ∆H° and correct classification as endothermic or exothermic? (LO 9.8) Process (a) Ammonium nitrate dissolves in water, and the temperature of the solution decreases.
Problem 6b
Several processes are given in the table and labeled as endo- thermic or exothermic and given a sign for ∆H°. Which process is labeled with the correct sign of ∆H° and correct classification as endothermic or exothermic? (LO 9.8) Process (b) Methane, the main component of natural gas, is burned to produce a flame on a stovetop.
Problem 6c
Several processes are given in the table and labeled as endo- thermic or exothermic and given a sign for ∆H°. Which process is labeled with the correct sign of ∆H° and correct classification as endothermic or exothermic? (LO 9.8) Process (c) Water freezes into ice in the freezer.
Problem 6d
Several processes are given in the table and labeled as endo- thermic or exothermic and given a sign for ∆H°. Which process is labeled with the correct sign of ∆H° and correct classification as endothermic or exothermic? (LO 9.8) Process (d) Rubbing alcohol evaporates from your skin.
Problem 7
How much heat is required to raise a 50.0 g piece of iron from 25 °C to its melting point of 1538 °C? The specific heat capacity for iron is 0.451 J/g•°C. (a) 34.1 kJ (b) 168 kJ (c) 12.1 kJ (d) 6.78 kJProblem 9
A 25.0 g piece of granite at 100.0°C was added to 100.0 g of water of 25.0°C, and the temperature rose to 28.4°C. What is the specific heat capacity of the granite? (The specific heat capacity for water is 4.18 J/(g•°C).) (LO 9.10) (a) 0.563 J/(g•°C) (b) 1.53 J/(g•°C) (c) 0.992 J/(g•°C) (d) 0.794 J/(g•°C)Problem 10
When 12.5 g of NH4NO3 is dissolved in 150.0 g of water of 25.0 °C in a coffee cup calorimeter, the final temperature of the solution of 19.7 °C. Assume that the specific heat of the solution is the same as that of water, 4.18 J/(g•°C). What is the ΔH per mol of NH4NO3? (LO 9.10) NH4NO3 (s) → NH4+ (aq) + NO3−(aq) ΔH = ? (a) +3.60 kJ (b) +23.0 kJ (c) +21.3 kJ (d) −3.60 kJ
Problem 11
Calculate the enthalpy change for the reaction C(s) + 2 H2(g) → CH4(g) ΔH = ? Given the enthalpy values for the following reactions CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l) ΔH = −890.4 kJ C(s) + O2(g) → CO2(g) ΔH = −393.5 kJ H2(g) + 1/2 O2(g) → H2O (g) ΔH = −285.8 kJ (a) −1569.7 kJ (b) +211.1 kJ (c) −1855.5 kJ (d) −74.7 kJProblem 12
A table of standard enthalpies of formation (ΔH°f) gives a value of −467.9 kJ/mol for NaNO3(s). Which reaction has a ΔH° value of −467.9 kJ? (a) Na+ (aq) + NO3−(aq) → NaNO3(s) (b) Na(s) + N(g + O3(g) → NaNO3(s) (c) Na(s) + 1/2 N2(g) + 3/2 O2(g) → NaNO3(s) (d) 2 Na(s) + N2(g) + 3 O2(g) → 2 NaNO3(s)Problem 13
What is ΔH for the explosion of nitroglycerin? (LO 9.14) 2 C3H5(NO3)3(l) → 3 N2(g) + 1/2 O2(g) + 6 CO2(g) + 5 H2O(g)
