Question

$20g$ water at${20}^{o}C$ is contained in a calorimeter. 10 g of water at ${50}^{o}C$ is mixed into it. Temperature of mixture would be :

• A. ${15.2}^{o}C$
• B. ${30}^{o}C$
• C. ${35.2}^{o}C$
• D. ${43.7}^{o}C$

Answer 1

The correct option is B ${30}^{o}C$

Let the final temperature be $T$,

Heat gained by cold water + calorimeter =heat lost by hot water.

so, $20\times 4.2\times (T-20)=10\times \times 4.2\times (50-T)$

Thus, $T={30}^{o}C$