10 minutes maximum

An IB Periodic Table is required.

1. Ethyne reacts with oxygen as shown here:

2C2H2 (g) + 5O2 (g)  4CO2 (g) + 2H2O(l)

Which of the following statements is correct?

• A.   The reaction is endothermic and ∆H is positive.
• B.   The reaction is endothermic and ∆H is negative.
• C.   The reaction is exothermic and ∆H is positive.
• D.   The reaction is exothermic and ∆H is negative.
2. Which one of the following statements is true about endothermic reactions?
• A.   The enthalpy change is always negative.
• B.   The products are always less stable than the reactants.
• C.   The chemical energies are converted to heat energies.
• D.   They always have low activation energies.
3. Which of the following equations represent the enthalpy change of formation of propene?
• A.   3C(g) + 6H(g)  C3H6(g)
• B.   C3H6(g) + 9/2 O2(g)  3CO2(g) + 3H2O(l)
• C.   3C(s) + 3H2(g)   C3H6(g)
• D.   C3H6(g) +9/2 O2(g)  3CO2(g) + 3H2O(g)
4. Which of the following equations represent the enthalpy change of combustion of pentan-1-ol?
• A.   5C(s) + 6H2(g)+ ½ O2(g)  CH3CH2CH2CH2CH2OH(l)
• B.   CH3CH2CH2CH2CH2OH(l) + 15/2 O2(g)  5CO2(g) + 6H2O(l)
• C.   5C(s) + 12H(g) + O(g)  CH3CH2CH2CH2CH2OH(l)
• D.   2CH3CH2CH2CH2CH2OH(l) + 15O2(g)  10CO2(g) + 12H2O(l)
5. A 27g aluminum block is heated from 18 oC to 68 oC and it absorbs 1215 J of energy. What is the molar specific heat capacity of aluminum in J mol-1 oC-1?
• A.   0.900
• B.   4.19
• C.   9.00
• D.   24.3

6. Which of the following reactions are exothermic?

 I. HCl(aq) + NaOH(aq)  → NaCl(aq) + H2O(l) II. 2C4H10(g) + 13O2(g)  → 8CO2(g) + 10H2O(l) III. CaCO3(s)  → CaO(s) + CO2(g)

• A.   I and II only
• B.   I and III only
• C.   II and III only
• D.   I, II and III

7. An experiment is carried out, as shown in the diagram, to measure the enthalpy change of combustion of cyclohexane.

Burning 0.5 g of the fuel increases the temperature of 100g of water by 35 oC.

The specific heat capacity of water is 4.18 J g-1 K-1.

Which of the following expressions calculates the enthalpy change of combustion of cyclohexane in kJ mol-1?

 A. $${0.5 \times 4.18 \times 35} \over{(100/84.18) \times 1000}$$ B. $${100 \times 4.18 \times 35} \over{(0.5/84.18) \times 1000}$$ C. $${100 \times 4.18 \times (35+273)} \over{(0.5/84.18) \times 1000}$$ D. $${100 \times 4.18 \times (35+273) \times 1000} \over{(0.5/84.18)}$$
8. The enthalpy change of solution of ammonium nitrate is given as +25.69 kJ mol-1 in the IB Chemistry data booklet. When 8.0 g of the salt is dissolved in 100 cm3 of water, what is the expected temperature change of the solution in oC? Assume the specific heat capacity of the solution is 4.2 J g-1 oC-1.
• A.   0.0061
• B.   0.45
• C.   2.1
• D.   6.1

9. The enthalpy change of the following reaction is -57 kJ mol-1:

HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)

Calculate the amount of heat energy released when 100.0 cm3 of 0.400 mol dm-3 hydrochloric acid reacts with 25.0 cm3 of 0.800 mol dm-3 sodium hydroxide solution.

• A.   1140J
• B.   2280J
• C.   1140kJ
• D.   2280kJ

10. 3.00g of zinc powder is measured with a scale and is added into 25cm3 of 1mol dm-3 copper(II) sulphate solution in a glass beaker. The starting temperature and maximum temperature of the reaction are measured using a digital thermometer, in order the calculate the enthalpy change of the reaction.

What is the best way to reduce the random error in this experiment?

• A.   Making a fresh solution of copper(II) sulphate using a volumetric flask.
• B.   Calibrating the balance before measuring the mass of zinc powder.
• C.   Repeating the experiment several times.
• D.  Replacing the glass beaker with a polystyrene cup.