10 minutes maximum

An IB Periodic Table is required.

1. Using the information below, what is the enthalpy change of reaction (∆rH) for the oxidation of SO2 to SO3?

 S(s) + O2(g)  → SO2(g) ∆rH = x S(s) + 3/2O2(g)  → SO3(g) ∆rH = y

• A.   x+y
• B.   x-y
• C.   -x+y
• D.  -x-y
2+3: The reduction of nitrogen monoxide by carbon monoxide is used industrially to remove both pollutants simultaneously in flue gas. The equation for this reaction is:

2NO + 2CO  → N2 + 2CO2

2. What is the enthalpy change of this reaction, ∆rH, given the following data?

 Enthalpy change of formation ∆fHo (kJ mol-1) NO(g) 90.3 CO(g) -110.5 CO2(g) -393.5

• A.   + (90.3) - (110.5) + (393.5)
• B.   + 2(90.3) - 2(110.5) + 2(393.5)
• C.   - (90.3) + (110.5) - (393.5)
• D.   - 2(90.3) + 2(110.5) - 2(393.5)
3. The reaction above can be accelerated using a copper-based catalyst. How does the enthalpy change of this reaction, ∆rH, change in the presence of a catalyst?
• A.   ∆rH becomes more endothermic.
• B.   ∆rH does not change.
• C.   ∆rH becomes more exothermic.

4. 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

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

 Enthalpy change of formation ∆fHo (kJ mol-1) C(s) -394 H2(g) -286 CH3COCH3(l) -1790

• A.  +1110
• B.  +250
• C.  -250
• D.  -3830

6. To indirectly determine the enthalpy change of reaction for the thermal decomposition of potassium hydrogencarbonate to potassium carbonate, both compounds are reacted with excess dilute hydrochloric acid individually, and the enthalpy change of each reaction is measured:

 KHCO3(s) + HCl(aq)  → KCl(aq)+H2O(l)+CO2(g) ∆H1 K2CO3(s)+2HCl(aq)  → 2KCl(aq)+H2O(l)+CO2(g) ∆H2

What is the enthalpy change for the following reaction, calculated using Hess’s Law?

2KHCO3(s)  → K2CO3(s)+ H2O(l)+CO2(g)

• A.   2∆H1-∆H2
• B.   ∆H1-∆H2
• C.   -∆H1+∆H2
• D.  -2∆H1+∆H2

7. On the potential energy profile below, the following reaction is shown:

M + N + O  → Q + R

P is an intermediate in this reaction.

Which arrow A to D in the diagram above shows the ∆H of the reaction?

8. Cyclohexene undergoes addition reaction with bromine to form 1,2-dibromocyclohexane. The equation for this reaction is:

Bond enthalpies are:

 Average Bond Energy (kJ mol-1) C-C 346 C=C 614 Br-Br 193 C-Br 285

What is the enthalpy change of this reaction, in kJ, calculated using the bond enthalpies given above?

• A.   -109
• B.   -31
• C.   +109
• D.  +176
9. Which of the following equations represent the bond enthalpy of H-Br?
• A.   H+(g) + Br-(g)  → HBr(g)
• B.   H(g) + Br(g)  → HBr(g)
• C.   HBr(g)  → ½H2(g) + ½Br2(g)
• D.   H2(g) + Br2(g)  → 2HBr(g)
10. The equation below shows the incomplete combustion of methanol:

CH3OH(l) + O2(g)  → CO(g) + 2H2O(l)

What is the enthalpy change calculated using the data given below?

 Approximate Average Bond Energy (kJ mol-1) C-H 410 C-O 360 C=O 800 CO triple bond 1070 O=O 500 O-H 460

and:

 CH3OH(l)  → CH3OH(g) ∆H = 35 kJ mol-1 H2O(l)  → H2O(g) ∆H = 44 kJ mol-1

• A.   -413 kJ mol-1
• B.   -369 kJ mol-1
• C.   -360 kJ mol-1
• D.   +351 kJ mol-1