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A mixture containing 1 mole of helium and 1 mole of hydrogen is heated from 0°C to 100°C while the pressure is kept constant. How much heat must be supplied?

1. 600 cal
2. 1200 cal
3. 1800 cal
4. 3600 cal

Correct answer: 1200 cal

Solution

Q = (n_He*Cp_He + n_H2*Cp_H2)*dT = (5/2 R + 7/2 R)*100 = 6R*100 = 600R. With R = 2 cal/mol/K, Q = 1200 cal.

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