Answer:
a) The temperature of the water will rise by maximum 100 K, steam by 143.9 K
b) The temperature of the water will rise by maximum 100 K, steam by 1077.45 K
c) The temperature of the water will rise by maximum 100 K, steam by 972.75 K
d) The temperature of the water will rise by maximum 100 K, steam by 1027.86 K
e) The temperature of the water will rise by maximum 100 K, steam by 902.6 K
Explanation:
a) ΔH for ethanol = 29.65 kJ/g therefore, burning 100 g will produce;
29.65 × 100 = 2965 kJ
The specific heat capacity of water = 4.184 J/(g·K)
Therefore, 2965000= 1000 × 4.184 × ΔT
ΔT = 2965000 ÷ (1000 × 4.184) = 708.65 K
Latent heat of water = 2260 kJ/kg will be absorbed when the temperature reaches the boiling point of water hence we have
2965 - 2260 = 705 kJ to heat the water of which a maximum of 418.4 will boil the water and the steam temperature will rise by (705-418.4)/1.996 = 143.59 K
b) For Hexane: ΔH = 48.29 kJ/g
100 g will produce 4829 kJ
∴ Temperature change for the 1 kg water is given as follows
ΔT = 4829000 ÷ (1000 × 4.184) = 1154.16 K
However
4829 - 2260 = 2569
2569 - 418.4 = 2150.6
2150.6 / 1.996 = 1077.45 K
The final steam temperature will rise by 1077.45 K
c) For Kerosene(C₁₂H₂₆): ΔH = 46.2 kJ/g
100 g will produce 4620 kJ
∴ Hypothetically the temperature change for the 1 kg water is given as follows
ΔT = 4620000 ÷ (1000 × 4.184) = 1104.21 K
However
4620 - 2260 = 2360
2360 - 418.4 = 1941.6
1941.6 / 1.996 = 972.75 K
The final steam temperature will rise by 972.75 K
d) For Car Fuel(90% octane): ΔH = 47.3 kJ/g
100 g will produce 4730 kJ
∴ Temperature change for the 1 kg water is given as follows
ΔT = 4730000 ÷ 4184 = 1130.5 K
However
4730 - 2260 = 2470
2470 - 418.4 = 2051.6
2051.6 / 1.996 = 1027.86 K
The final steam temperature will rise by 1027.86 K
e) For Diesel (C₁₂H₂₃): ΔH = 44.8 kJ/g
100 g will produce 4480 kJ
∴ Temperature change for the 1 kg water is given as follows
ΔT = 4480000 ÷ 4184 = 1070.75 K.
However
4480 - 2260 = 2220
2220 - 418.4 = 1801.6
1801.6 / 1.996 = 902.6 K
The final steam temperature will rise by 902.6 K.
