The heat produced on complete combustion of 20 g of a fuel could raise the temperature of 1.5 kg of water form `25^(@)C` to `75^(@)C`. Calculate the calorific value of the fuel if the specific heat capacity of water is `4.2 J g^(-1).^(@)C^(-1)`. Assume that the heat absorbed by the container is negligible.

Explanation

(i) Formula for calorific value, `Q = msDeltatheta`.
(ii) Find the amount of heat energy required to increase the temperature of 1.5 `mug` of water from `25^@C` to `75^@C` using the formula Q = ms
Let .s. denote specific heat capacity of water and `.Deltatheta.` denote change in the temperature.
Is this heat energy released due to complete combustion of 20 g of a fuel?
Then, the formula related to combustion of fuel is Q = m.k.
Q = m.k = mwst, since heat released in combustion is absorbed by water.
Thus, find the value of .k. .
(iii)`"15.75 kJ g"^(-1)`