# Arrhenius Questions with answers

- Created by: Aaron
- Created on: 03-03-13 12:57

First 308 words of the document:

Arrhenius revision Questions

1. Calculate the rate constant using the Arrhenius equation given the following values

for a reaction : A = 2.22 x 1011 moldm-3s-1 ; Ea = 111 kJmol-1 ; T = 444 oC

2. The rate constant for the between Mg and HCl was measured at different temperatures. The

results obtained were:

T(K) 290 310 330 350

k (moldm-3s-1) 0.0030 0.0216 0.122 0.567

Use the Arrhenius equation to calculate the pre-exponential factor at 290K if the activation energy

was 55.5 kJmol-1

Q3. A series of experiments were carried out to investigate the effect of temperature on the rate

of reaction

(i) Complete the missing data in the table below.

Temperature (T) / K 1/ temperature (1/T) / K1 Rate constant ln (rate constant)

295 3.39 × 10 3

2.88 × 10 3

5.85

305 3.28 × 103 1.01 × 102 4.60

311 1.83 × 102

320 3.13 × 103 4.98 × 102 3.00

333 3.00 × 103 2.02 × 101 1.60

(ii) Plot a graph of ln (rate constant) on the vertical axis against 1/T on the horizontal axis

(iii) Use the Arrhenius equation together with your graph to calculate a value of the activation energy,

EA, for this reaction. Show all steps in your working. Include units in your final answer, which should be

given to two significant figures.

.....................................................................................................................

Answers

Q1 k = A exp(- Ea/RT) ; k = 2.22 x 1011 x exp(- 111,000/8.31 x 717)

k = = 2.22 x 1011 x 8.11486193.. x 10-9 = 180 moldm-3s-1 (to 3 sig fig)

Q2 k = A exp(- Ea/RT) ; 0.0030 = A x exp(- 55,500/8.31 x 290)

0.0030 = A x 9.95858...... x 10-11 A = 3.01 x 107 moldm-3s-1 (to 3 sig fig

Q3 (i) 3.22 × 103 ; -4.00 correct sig fig needed for 1 mark eg -4 = no mark

(ii) labelled axis, sensible scale = 1 ;

correct plotting and good line of best fit (no double / broken/ thick lines ) =1

(iii) Gradient = - 10823 K; [ allow range -11200 to -10400 ] (unit not needed for mark )

Ea = 10823 x 8.31 = (+) 889939 J mol-1 (1)

= 90 kJmol-1 or 90,000 J mol-1 to 2 sig fig (1) (no unit = no mark)

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