Question

5 kg of ice at $-10{}^{o}C$ is added to 5 kg of water at $10{}^{o}C$. The temperature of the resulting mixture will:

• A. $-10{}^{o}C$
• B. $0{}^{o}C$
• C. $3.3{}^{o}C$
• D. $10{}^{o}C$

Answer 1

The correct option is B $0{}^{o}C$

Let t be the resultant temperature.
Heat required to convert 5 kg of ice at $-10{}^{o}C$ into ice at $0{}^{o}C$
$=5kg\times 2100Jk{g}^{-1}\times 10{}^{o}C$
$=105000J$
Heat lost by 5 kg of water at $10{}^{o}C$ to form 5 kg of ice at $0{}^{o}C$
$=5\times 4200\times 10$
$=21000J$
$\therefore$ Heat lost is less than heat gain. So, the resultant temperature is $0{}^{o}C$