Physics (AS & A Level) · Feb / March 2016 · Paper 42 · Question 2
9702
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2(a)(i)[2]
sum of kinetic and potential energy of atoms/molecules reference to random (distribution) [2]
2(a)(ii)[1]
no forces (of attraction or repulsion) between molecules [1]
2(b)[3]
pV = NkT or pV = nRT and R = kNA , n = N / NA 1/3 Nm<c 2> = NkT or 1/3 m<c 2> = kT <EK> = 1/2 m<c 2> so <EK> = 3/2 kT [3]
2(c)(i)[2]
<EK> = 3/2 × 1.38 × 10–23 × (273 + 12) = 5.9 (5.90) × 10–21 J [2]
(use of T = 12 K not T = 285 K scores 0 / 2)
2(c)(ii)[2]
number = (17 / 32) × 6.02 × 1023 = 3.2 (3.20) × 1023 [2]
2(c)(iii)[1]
internal energy = 5.9 × 10–21 × 3.2 × 1023 = 1900 (1890) J [1]
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