Question

A.) calculate the heat change in kilocalories for condensation of 3.5 kg of steam at 100 Celsius.(Express your answer as a positive value using two significant figures and include the appropriate units)

B.) calculate the heat change in kilojoules for condensation of 185 g of steam at 100 Celsius.

(Express your answer as a positive value using three significant figures and include the appropriate units)

Answer 1

each gram of water at 100° C at ordinary pressures can absorb up to 540 calories without changing its temperature as the heat absorbed is used to break the hydrogen bonds among the water molecules and not to change the temperature. This means that 1 gram of water at 100° C changes to 1 gram of steam at 100° C by absorbing 540 calories.

A) So 3500gm of steam wll reqiure 3500*540=1890 kilocalories = 19*10^2 kilocalories approximatey

B) 1Joule = 0.239 gram calories

185g of stteam will release 185*540=99900 caloires = 417.9816 kilojoules =418 kilojoules