IBDP Practice Worksheet 31/01/22
1. Identify the missing reaction required to solve for the enthalpy of the unknown
equation below using Hess’s Law:
2A+B→A2B
ΔH=x−y
Given: 2A+C→A2C ΔH=x
2. Calculate the enthalpy change, in kJ mol−1, involved for the reaction below,
C2H4(g)+H2(g)→C2H6(g) ΔH=?
given the following reaction equations.
H2(g)+ 1/2 O2(g) →H2O(l) ΔH=−286kJmol−1
C2H6(g)+3 ½ O2(g) →2CO2(g)+3H2O(l) ΔH=−1561kJmol
C2H4(g)+3O2(g) →2CO2(g)+2H2O(l) ΔH=−1411kJmol−1
Give the answer to three significant figures (no unit required).
3.
Calculate the enthalpy change, in kJ mol−1, for the reaction above, given the
following single bond enthalpy values, in kJ mol−1, at 298 K. Units are not required in the
answer.
C
H
Br
C
346
414
285
H
414
436
366
Br
285
366
193
The bond enthalpy for C=C is 614 kJ mol−1.
4.To calculate the enthalpy change of a reaction using average bond enthalpies, the
equation is:
∆H = ∑(bond enthalpies of ______ ; Your answer here;) – ∑(bond enthalpies of ______ ;
Your answer here;).
Write the two missing words with a space between them without punctuation.
5. The equation for the formation of ethene from its elements is shown below:
2C (s) + 2H2 (g) → C2H4 (g)
Determine the standard enthalpy of formation of ethene, ΔHf, in kJ mol-1, given the
following three equations and their enthalpy change of combustion values, ΔHc.
C (s) + O2 (g) → CO2 (g)
ΔHc = –394 kJ
H2 (g) + ½O2 (g) → H2O (g)
ΔHc = –286 kJ
C2H4 (g) + 3O2 (g) → 2CO2 (g) + 2H2O (g)
ΔHc = –1393 kJ
Give the answer to two significant figures (no units required).
6.Consider the following bond enthalpies:
Bond
Bond enthalpy (kJ mol−1)
C=C
615
C−F
484
C−C
348
F−F
158
Calculate the enthalpy change (in kJ mol−1) for the addition reaction between fluorine
and ethene (in the gaseous state)?
C2H4 (g) + F2 (g) → CH2FCH2F (g)