# School of Science and Mathematics

## Unit 2.3 General & Environmental Chemistry, lectures 2,3 &4

Lecture 2

Problem 5

a) 1 mmHg = 101325 Pa/760 = 133.3 Pa

b) 28.3 mmHg = 3773 Pa

Problem 6

a) 2200 Pa

b) 220 000 Pa

c) 330.3 Pa

Problem 7

a) 800.5 kJ

b)
D V = 40
L = 0.040 m3
p = 0.25 x 101325 Pa = 25331 Pa
\ w = 1013.25 J

Problem 8

a) final speed = 96 kmh = 96000 m /3600 s = 26.67 m/s
acc’n = 26.67 m/s / 4 s = 6.67 m/s2 = 0.68 "gravities"

b) 250 kg x 9.81 m.s-2 x 2 m = 4905 N.m = 4905 J

c) w = 2 x 101325 Pa x 5 x 10-4 m2 x 0.3 m = 30.4 J

d) 706.5 kPa : 6.97 i.e. 7 atm

Problem 9

done in class

Problem 10

a)
10 dm = 1 m
100 dm2 = 1 m2
1000 L = 1 m3

b) 20

c) 104cm2 = 1 m2
106 cm3 = 1 m3

Problem 11

R = 8.313 J.mol-1K-1

Problem 12

n = 0.0157 mol

Lecture 3

Problem 13

a) 62.4 J
b) 334.4 kJ
c) 16.72 GJ

Problem 14

Note use of units

heat cap. = 9.201 J / 1.652 ° C = 5.5696 J/° C
spec. heat cap. = (5.5696 J/° C) / 2.311 g = 2.410 J.° C-1.g-1 = 2.410 J.K-1.g-1

molar heat cap = 2.410 J.K-1.g-1 x 46.07 g.mol-1 = 111.0 J.K-1.mol-1

Lecture 4

Problem 15

2Cgraphite + 3H2,g + ½ O2,g = C2H5OHl
4Cgraphite + 4H2,g + O2,g = CH3.COOC2H5,l
H2,g + ½ O2,g = H2Ol
Bas + Ss + 2 O2,g = BaSO4,s

Problem 16

2Cgraphite + 3H2,g = C2H6,g
D Hcombust = 2 x D Hf(CO2,g) + 3 x D Hf(H2Ol) - D Hf(C2H6,g)
gives D Hf(C2H6,g) = -84.6 kJ/mol

Problem 16

CH3CHOl

formation: 2Cgraphite + 2H2,g + ½ O2,g = CH3CHOl

combustion: CH3CHOl + 2½ O2,g = 2 CO2,g + 2 H2Ol etc.

Problem 17

D H = 43.05 kJ/mol

Problem 18

a) D Hf(glycine) = -536.6 kJ/mol
b) D HRx = + 41.4 kJ/mol (endothermic)

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