Thermodynamics Question 238

Question: A cube of side 5 cm made of iron and having a mass of 1500 g is heated from 25C to 400C. The specific heat for iron is 0.12cal/gC and the coefficient of volume expansion is 3.5×105/C, the change in the internal energy of the cube is (atm pressure 1×105N/m2 )

Options:

A) 320 kJ

B) 282 kJ

C) 141 kJ

D) 423 kJ

Show Answer

Answer:

Correct Answer: B

Solution:

[b] Q=mCΔr=1.5×0.12×4200×(40025)

=2.83×105J

W=P(ΔV)=P(VΔT)

=105×(5×102)3×3.5×105×375=0.164J

Thus Q=ΔU+W

or2.83×105=ΔU+0.164;ΔU=282kJ



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