Question

How much heat is required to convert $10g$ of ice at $-5^{o}C$ into steam at ${100}^{o}C$

• A. $5151cal$
• B. $4672cal$
• C. $7226cal$
• D. $6000cal$

Answer 1

Answer: (C)

$7226cal$

Given : How much heat is required to convert 10g10g of ice at $-5^{o}C$ into steam at ${100}^{o}C$

$m=10g$

Specific heat of ice=0.5

Latent heat of fusion from ice to water L=80cal

Specific heat of water=1

Latent heat of vaporization L=540cal

Solution :

Case 1

Heat required to convert ice at $-5^{o}C$ to $0^{o}C$

$Q_1=mS\Delta T$ $\Rightarrow$ $Q_1=10\times 0.5\times 5$ $\Rightarrow$ $Q_1=25cal$

Case 2

Heat required to convert ice into water at $0^{o}C$

$Q_2=mL$ $\Rightarrow$ $Q_2=10\times 80$

$Q_2=800cal$

Case 3

Heat required to convert water from $0^{o}Cto{100}^{o}C$

$Q_3=mS\Delta T$ $\Rightarrow$ $Q_3=10\times 1\times 100$

$Q_3=1000cal$

Case 4

Heat required to convert water into steam at ${100}^{o}C$

$Q_4=mL$ $\Rightarrow$ $Q_4=10\times 540$

$Q_4=5400cal$

Total heat required $Q_{total}=Q_1+Q_2+Q_3+Q_4$

$Q_{total}=25+800+1000+5400$

$Q_{total}=7225cal$