Question

How much heat is required to change 5 gram ice ( $0^\circ C$ ) to steam at $100^\circ C$ ? Latent heat of fusion and vaporization for water are 80 cal/g and 540 cal/g respectively. Specific heat of water is 1 cal/g/k.

• A. 7200 cal
• B. 3600 cal
• C. 1800 cal
• D. 900 cal

Answer 1

Answer: (B)

$\underset{\left(\right. 0 ^\circ C \left.\right)}{I c e}\overset{q_{1}}{ \rightarrow }\underset{\left(\right. 0 ^\circ C \left.\right)}{W a t e r}\overset{q_{2}}{ \rightarrow }\underset{\left(\right. 100 ^\circ C \left.\right)}{W a t e r}\overset{q_{3}}{ \rightarrow }\underset{\left(\right. 100 ^\circ C \left.\right)}{V a p o u r}$
$q=q_{1}+q_{2}+q_{3}$
$=\left(\right.80\times 5+msdT+540\times 5\left.\right)$ cal
$=\left(\right.80\times 5+5\times 1\times 100+540\times 5\left.\right)$ cal
$=3600$ cal