Question

If water of mass 20 g at $0{}^{o}C$ is mixed with 40 g of water at $10{}^{o}C$, then the final temperature of the mixture is $10{}^{o}C$

• A. True
• B. False

Answer 1

The correct option is B False

$\because q_{lost}=q_{gain}$

Let the final temperature be $x$

$q=m{C}_P△t\Rightarrow 20\times {10}^{-3}\times (x-0)\times 4.814=40\times {10}^{-3}\times (10-x)\times 4.814\Rightarrow 20\left(x\right)=40(10-x)\Rightarrow 20x=400-40x\Rightarrow 60x=400\Rightarrow x=6.667℃$

So, the final temperature is $6.667℃$ not $10℃$