10-minute Quiz : Ch34 Standard enthalpy changes of reactions

Which of the following are the standard conditions for measuring enthalpy change?

(1) A temperature of 298 K

(2) A pressure of 1 atm

(3) Using one mole of each reactant

• A. (1) and (2) only
• B. (1) and (3) only
• C. (2) and (3) only
• D. (1), (2) and (3)

Consider the thermochemical equation as shown. Which of the following statements are correct?

(1) The reaction is exothermic.

(2) The equation represents the standard enthalpy change of formation of nitric acid.

(3) The standard enthalpy change of the reaction: 2HNO₃(l) → N₂O₅(g) + H₂O(l) is +77.0 kJ mol⁻¹.

• A. (1) and (2) only
• B. (1) and (3) only
• C. (2) and (3) only
• D. (1), (2) and (3)

Which of the following equations represents the standard enthalpy change of formation of calcium bromide?

• A. Ca(s) + Br₂(g) → CaBr₂(aq)
• B. Ca(s) + Br₂(g) → CaBr₂(s)
• C. Ca(s) + Br₂(l) → CaBr₂(aq)
• D. Ca(s) + Br₂(l) → CaBr₂(s)

The standard enthalpy changes of formation of graphite and diamond are 0 kJ mol⁻¹ and +1.9 kJ mol⁻¹ respectively. Which of the following statements is/are correct?

(1) Graphite is energetically more stable than diamond.

(2) Graphite has higher energy content than diamond.

(3) The C−C bonds in graphite are weaker than those in diamond.

• A. (1) only
• B. (2) only
• C. (1) and (3) only
• D. (2) and (3) only

Which of the following is the standard state of iodine?

• A. I₂(g)
• B. I₂(l)
• C. I₂(s)
• D. I₂(aq)

Which of the following expressions gives the mass (in g) of ethanol needed to produce 209.6 kJ of heat upon complete combustion?

• A. 209.6/(1367 × 60.0)

• B. 1367/(209.6 × 60.0)

• C. (209.6 × 60.0)/1367

• D. (1367 × 60.0)/209.6

In an experiment, 50 cm³ of 1.0 M CH₃COOH(aq) is mixed with 50 cm³ of 1.0 M NaOH(aq) in a simple calorimeter. The maximum temperature rise of the reaction mixture is 4.6°C. What is the enthalpy change of neutralization between CH₃COOH(aq) and NaOH(aq)?

(Assume that the specific heat capacity and density of the reaction mixture are the same as those of water, i.e. 4.2 J g⁻¹ K⁻¹ and 1.0 g cm⁻³ respectively.)

• A. −19.3 kJ mol⁻¹
• B. −29.0 kJ mol⁻¹
• C. −38.6 kJ mol⁻¹
• D. −57.3 kJ mol⁻¹

The enthalpy change of neutralization can be determined by adding hydrochloric acid to 50 cm³ of 1 M sodium hydroxide solution. The graph shows the temperature of the reaction mixture during the experiment. What is the maximum temperature rise of the reaction mixture?

• A. (T₁ + T₂)/2

• B. T₂

• C. T₃

• D. (T₁ + T₃)/2

The temperature of 5 cm³ of a strong acid increases by 10°C when 5 cm³ of a strong alkali of the same concentration is added to it. What will be the temperature rise if 10 cm³ of each solution are mixed?

• A. 5°C
• B. 10°C
• C. 15°C
• D. 20°C

Consider the following reaction.

2CO(g) + O₂(g) → 2CO₂(g)　　ΔH = −566 kJ mol⁻¹

How much heat is released when 14.0 g of carbon monoxide is burnt completely?

(Relative atomic masses: C = 12.0, O = 16.0)

• A. 1132 kJ
• B. 566 kJ
• C. 283 kJ
• D. 142 kJ