Question

Calculate the specific heat of Ethanol. It requires 3,080 cal to raise 100 g of solid ethanol to at 156 K to liquid Ethanol at 166 K. If Ethanol melts at 156 K and has a latent heat of fusion of 25 cal/g.

• A. 0.58 cal/g.K
• B. 1.7 cal/g.K
• C. 2.5 cal/g.K
• D. 3.1 cal/g.K
• E. 5.8 cal/g.K

Answer 1

Answer: (A)

0.58 cal/g.K

$\underset{156K}{Solid}$ ethanol $\underset{Q_1}{\overset{}{\to }}$ $\underset{166K}{Solid}ethanol$ $\underset{Q_2}{\overset{}{\to }}$ $\underset{166K}{liquid}ethanol$

Given : $T_m=166$ K $m=100$ g $L_f=25$ cal/g $Q=3080$ cal $T^{\prime }=156$ K

Let the specific heat heat of ethanol be $S$.

Total heat required $Q=Q_1+Q_2=mS(T_m-T^{\prime })+m{L}_f$

$\therefore$ $3080=100\times S(166-156)+100\times 25$

OR $100\times S\left(10\right)=3080-2500$ $⟹S=0.58$ cal/g.K