Page 739 - SUBSEC October 2017_Neat

02238020/CAPE SPEC/MS/2017
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Question 3 KC UK XS

(e) 5
(i) For plotting graph

Suitable scales (1)
5-6 correct points (3)
3-4 correct points(Award 2 marks only)
1-2 correct points (Award 1 mark only)
<2 correct points (Award 0 marks)
Best fit line (1)

(ii) Half-life = 144 min   = 0.693 (1) 1
144 x 60

(iii) 900 min = 900 = 6.25 half-lives.
144
T ½ = 174 min
= 174 x 60 sec
= 10440 sec (1)

 = 0.693
T ½

= 0.693
10440 3

-5
= 6.6 x 10 (1)

A = Aoe - t

After 900 mins i.e. 900 x 60 sec
= 54000 sec
- 6.6 x 10 x 54000
-5

Activity = 3100 x e

= 3100 x e - 3.564

= 87.4 cpm (1)

Total 30 marks

10 15 5