Target: 10 Questions in 10 minutes

An IB Chemistry data booklet is helpful
1. Which of the following equations represent the standard enthalpy change of combustion of ethane?
  • A.   2C(s) + 3H2(g)  → C2H6(g)
  • B.   C2H4(g) + H2(g) → C2H6(g)
  • C.   C2H6(g) + 3.5O2(g) → 2CO2(g) + 3H2O(l)
  • D.   2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(l)
2. 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)

3. Octane, C8H18, is a component in petrol. What is the enthalpy change of combustion of octane in kJmol-1 given the following data?

  Enthalpy change of formation
∆fHo (kJ mol-1)
C8H18(l) -250
CO2(g) -394
H2O(l) -286
 
  • A.   -5976
  • B.   -5476
  • C.   -430
  • D.   +430

4. Calculate the enthalpy change of formation of propanone, in kJ mol-1, given the following enthalpy change of combustion data:

  Enthalpy change of combustion
∆cHo (kJ mol-1)
C(s) -394
H2(g) -286
CH3COCH3(l) -1790
 
  • A.  +1110
  • B.  +250
  • C.  -250
  • D.  -3830
5. Ammonium perchlorate (NH4ClO4) is used as a solid oxidizer in modern booster rockets. It decomposes to provide oxygen according to the following equation:

4NH4ClO4(g)   → 4HCl(g) + 2N2(g) + 5O2(g) + 6H2O(g)

What is the heat released per mole of ammonium perchlorate given the following data?

  Enthalpy change of formation
∆fHo (kJ mol-1)
NH4ClO4(g) -295.8
HCl(g) -92.3
H2O(g) -241.8
  • A.  -38.3 kJ
  • B.  -159.2 kJ
  • C.  -636.8 kJ
  • D.  -750.8 kJ

6. Using the information given below, what is the enthalpy change of reaction for the thermite reaction shown in this equation?

2Al(s) + Fe2O3(s)   → 2Fe(l) + Al2O3(s)

∆fHo of Fe2O3(s) = -825.5 kJ mol-1
∆fHo of Al2O3(s) = -1675.7 kJ mol-1
Enthalpy change of melting of Fe = +13.8 kJ mol-1
 
  • A.  -822.6 kJ
  • B.  -850.2 kJ
  • C.  -877.8 kJ
  • D.  +850.2 kJ

7. Given the following standard enthalpy changes of formation:

  Enthalpy change of formation
∆fHo (kJ mol-1)
NO(g) +90.3
NO2(g) +33.1
N2O4(g) +9.1

which of the following reactions are exothermic?

I. N2(g) + O2(g) ⇌ 2NO(g)
II. 2NO(g) + O2(g) ⇌ 2NO2(g)
III. 2NO2(g) ⇌ N2O4(g)
 
  • A.   II only
  • B.   III only
  • C.   I and III only
  • D.  II and III only
8. The enthalpy change for the process ½Cl2(g) + e-  → Cl-(g) is equal to...
  • A.   the first electron affinity of chlorine
  • B.   the bond enthalpy of chlorine
  • C.   the 1st ionization energy of chlorine plus the bond enthalpy of chlorine
  • D.   the first electron affinity of chlorine plus the enthalpy change of atomization of chlorine

9. The Born-Haber cycle can be used to calculate the theoretical lattice enthalpy of unstable compounds. Given the following data, what is the lattice enthalpy of MgCl? (Note: NOT MgCl2).

Enthalpy change of formation of MgCl (kJ mol-1) -94
Enthalpy change of atomization of Mg (kJ mol-1) +147
Bond enthalpy of Cl2 (kJ mol-1) +242
1st ionization energy of Mg (kJ mol-1) +738
2nd ionization energy of Mg (kJ mol-1) +1451
1st electron affinity of Cl (kJ mol-1) -349
 
  • A. +335 kJ
  • B. +751 kJ
  • C. +872 kJ
  • D. +2202 kJ

10. Which of the following enthalpy changes is always endothermic?

I. 2nd ionization energy
II. 1st electron affinity
III. Enthalpy change of solution
  • A.   I only
  • B.   I and III only
  • C.   II and III only
  • D.   I, II and III