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.