1.
State what is meant by enthalpy change.
[1 mark]
- heat change at constant pressure
JD SCIENCE
Kinetics, equilibria and redox
Indicative marking points. Award marks for equivalent scientific or mathematical wording. Do not issue this sheet with the student worksheet.
2.
State what is meant by Hess's law.
[1 mark]
- total ΔH independent of route
3.
State what is meant by mean bond enthalpy.
[1 mark]
- mean energy to break 1 mol of a bond
4.
State what is meant by collision theory.
[1 mark]
- E ≥ Ea and orientation
5.
State what is meant by rate equation.
[1 mark]
- rate = k[A]ᵐ[B]ⁿ
6.
State what is meant by equilibrium constant Kc.
[1 mark]
- products/reactants with powers of moles from equation
7.
State what is meant by Le Chatelier.
[1 mark]
- system opposes a change
8.
State what is meant by a Born–Haber cycle.
[1 mark]
- lattice enthalpy from Hess
9.
State what is meant by entropy.
[1 mark]
- measure of disorder
10.
State what is meant by the rate-determining step.
[1 mark]
- slowest step
11.
Devon is asked about enthalpy change in a Edexcel Chemistry paper.
(a) [2 marks]
- ΔH, kJ mol⁻¹
(b) [3 marks]
- exo negative
12.
Devon is asked about Hess's law in a Edexcel Chemistry paper.
(a) [2 marks]
- cycles
(b) [3 marks]
- formation and combustion data
13.
Devon is asked about mean bond enthalpy in a Edexcel Chemistry paper.
(a) [2 marks]
- gas states
(b) [3 marks]
- not exact for one molecule
14.
Devon is asked about collision theory in a Edexcel Chemistry paper.
(a) [2 marks]
- Maxwell–Boltzmann
(b) [3 marks]
- catalysts lower Ea
15.
Devon is asked about rate equation in a Edexcel Chemistry paper.
(a) [2 marks]
- orders from experiment
(b) [3 marks]
- k depends on T
16.
Devon is asked about equilibrium constant Kc in a Edexcel Chemistry paper.
(a) [2 marks]
- only T changes K
(b) [3 marks]
- no units sometimes
17.
Q=mcΔT. 100 g, c=4.18, ΔT=5.0
[3 marks]
- Final answer: 2090 J
18.
ΔH = −Q/n. Q=2090 J, n=0.010
[3 marks]
- Final answer: −209 kJ mol⁻¹
19.
Kc = [C]²/[A][B]. If all conc=2
[3 marks]
- Final answer: 2
20.
A first-order half-life is 20 s. k
[3 marks]
- Final answer: 0.0347 s⁻¹ (ln2/t½)
21.
Bonds broken 1200, made 1500. ΔH
[3 marks]
- Final answer: −300 kJ
22.
If T doubles and k increases, Ea is
[3 marks]
- Final answer: overcome by more particles / Arrhenius
23.
Devon carries out a Edexcel-style required practical linked to energetics, kinetics and equilibria. This is a typical Edexcel required-practical style question.
(a) [2 marks]
- Independent: the independent variable for this topic
- Dependent: the measured outcome
(b) [2 marks]
- keep all other variables constant
- so the test is fair / only one variable is changed
(c) [2 marks]
- repeat and calculate a mean / use a tighter method
24.
Devon carries out collecting valid data for energetics, kinetics and equilibria. This is a typical Edexcel required-practical style question.
(a) [2 marks]
- Independent: a chosen factor
- Dependent: a quantitative measurement
(b) [2 marks]
- calibrated instrument
- so the test is fair / only one variable is changed
(c) [2 marks]
- systematic error from zero error
25.
Devon carries out drawing a graph for energetics, kinetics and equilibria. This is a typical Edexcel required-practical style question.
(a) [2 marks]
- Independent: x-variable
- Dependent: y-variable
(b) [2 marks]
- same scale / same apparatus
- so the test is fair / only one variable is changed
(c) [2 marks]
- not drawing a line of best fit through the trend
26.
Devon carries out evaluating a method about energetics, kinetics and equilibria. This is a typical Edexcel required-practical style question.
(a) [2 marks]
- Independent: method change
- Dependent: precision / accuracy
(b) [2 marks]
- same sample size
- so the test is fair / only one variable is changed
(c) [2 marks]
- too few repeats
27.
Compare enthalpy change with Hess's law.
[4 marks]
- heat change at constant pressure
- total ΔH independent of route
- give one linked difference
28.
Compare Hess's law with mean bond enthalpy.
[4 marks]
- total ΔH independent of route
- mean energy to break 1 mol of a bond
- give one linked difference
29.
Compare mean bond enthalpy with collision theory.
[4 marks]
- mean energy to break 1 mol of a bond
- E ≥ Ea and orientation
- give one linked difference
30.
Compare collision theory with rate equation.
[4 marks]
- E ≥ Ea and orientation
- rate = k[A]ᵐ[B]ⁿ
- give one linked difference
31.
Apply your knowledge of Le Chatelier to this situation: used with K to explain yield
[3 marks]
- used with K to explain yield
32.
Apply your knowledge of a Born–Haber cycle to this situation: formation, atomisation, ionisation, EA
[3 marks]
- formation, atomisation, ionisation, EA