Question

How much amount of heat is required to raise the temperature of $100g$ of water from ${30}^{\circ }C$ to ${100}^{\circ }C$? The specific heat of water = 4.2 J ${g^{-1}}^{\circ }{C}^{-1}$.

• A. $25.5kJ$
• B. $29.4kJ$
• C. $30kJ$
• D. $40kJ$

Answer 1

The correct option is B $29.4kJ$

Given , $m=100g,{\theta }_1={30}^{0}C,{\theta }_2={100}^{0}C$

We have , specific heat of water $c=4.2J/g{-}^{o}C$

Now , heat required to raise the temperature of water is given by the definition of specific heat c ,

$Q=mc\Delta \theta =mc({\theta }_2-{\theta }_1)$

or $Q=100\times 4.2\times (100-30)=29400J=29.4kJ$