1) A 50.0 g glass container contains 200 g of water all at 20.0°C. A 20.0 g piec

Question

1) A 50.0 g glass container contains 200 g of water all at 20.0°C. A 20.0 g piece of an alloy at 100°C is added to the water in the container. The final temperature of the mixture is 24°C. What is the specific heat of the alloy, in cal/gm °C? (specific heat of water = 1.00 cal/gm °C, specific heat of glass = 0.200 cal/gm °C)
A) 2.75
B) 1.87
C) 1.54
D) 0.852
E) 0.553

2) A sample of helium has a volume of 2.00 liters, a temperature of 20.0°C, and a pressure of 2.50 atmospheres. What is the energy needed to heat at constant volume the sample of helium gas from 20.0°C to 95.0°C?
A) 88.0 J
B) 137 J
C) 175 J
D) 207 J
E) 476 J

Explanation / Answer

mwsw(24-20)+ mgsg(24-20)=masa(100-24)

20*0.2*4 +100*1*4 =20*sa*76

sa=0.553 (E) IS CORRECT

(b)

V=2L

P=2.5ATM

T=293 K

R=0.082

Therefore,

n=0.223

C=1.5*8.313

Heat needed= nCdT

                   =0.223*1.5*8.313*(95-20)

                    =207 Joules (D)

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