Calculate the energy change for a pure substance over a temperature range.?

[匿名]

2018-01-22 1:51 pm

The following information is given for water at 1 atm:

Tb= 100.00 C
Tm= 0.00 C
Specific heat solid = 2.100 J/g °C
Specific heat liquid = 4.184 J/g °C
delta vap (100.00 C)= 2.259x10^3 J/g
delta fus (0.00 C)= 333.5 J/g
A 39.50 g sample of solid water is initially at –30.00°C. If the sample is heated at constant pressure (P = 1 atm),________kJ of heat are needed to raise the temperature of the sample to 25.00°C.

回答 (1)

wanszeto

2018-01-22 2:53 pm

Heat required to raise temperature = m c ΔT
Heat required to change physical state = m L

Heat required to change 39.50 g solid water from -30.00°C to O.00°C
= (39.50 g) × (2.100 J/g °C) × (30.00°C)
= 2488.5 J

Heat required to melt 39,50 g solid water to liquid water at 0.00°C
= (39.50 g) × (333.5 J/g)
= 13173.25 J

Heat required to change 39.50 g liquid water from 0.00°C to 25.00°C
= (39.50 g) × (4.184 J/g °C) × (25.00°C)
= 4131.7 J

Total heat required
= (2488.5 + 13173.25 + 4131.7) J
= 19790 J (to 4 sig, fig.)

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