Question

Ethyl alcohol has a latent heat of vaporization of 850 J/g. Water has a latent heat of vaporization of 2260 J/g. Container A contains 1.0 kg of ethyl alcohol. Container B contains 1.0 kg of water. Both liquids are brought to a boil. If the same amount of heat is continuously added to each container, which liquid will boil away first?

a ) water
b ) ethyl alcohol
c ) both will boil away at the same time
d )boiling and condensation will happen at the same rate so neither liquid will boil away

Answer 1

Answer:

b) Ethyl alcohol

Explanation:

Let’s calculate the amount of heat required to boil away each liquid.

$q = m\Delta_{\text{vap}}H$

Ethyl alcohol: $q = \text{1000 g} \times \frac{\text{850 J} }{\text{1 g}} = 8.50 \times 10^{5} \text{ J}$

Water: $q = \text{1000 g} \times \frac{\text{2260 J} }{\text{1 g}} = 2.26 \times 10^{6} \text{ J}$

If we are supplying heat at a constant rate, we will have provided enough to evaporate all the ethyl alcohol while the water is still boiling.

The ethyl alcohol will boil away first.

Evaporation and condensation occur at the same rate only in a closed system .