Question

Two liquids at temperatures ${60}^{o}C$ and ${20}^{o}C$ respectively have masses in the ratio 3:4 and their specific heats in the ratio 4:5. If the two liquids are mixed, the resultant temperature is :

• A. ${70}^{o}C$
• B. ${40}^{o}C$
• C. ${50}^{o}C$
• D. ${35}^{o}C$

Answer 1

The correct option is D ${35}^{o}C$

Heat lost by one liquid $=$ Heat gained by another liquid
$m_1.C_1.\Delta T_1=m_2.C_2.\Delta T_2$
$\frac{m_1}{m_2}\times \frac{C_1}{C_2}=\frac{T-20}{60-T}$
$\frac{3}{4}\times \frac{4}{5}=\frac{T-20}{60-T}$
$180-3T=5T-100$
$8T=280$
$T={35}^{o}C$