A puddle holds 190 g of water.If 1.0 g of water evaporates from the surface,what is the approximate temperature change of the remaining water? (L_v = 540 cal/g)

Question

Quizplus · Accepted Answer

The amount of heat required to evaporate 1.0 g of water is: 
Heat = 540 cal/g x 1.0 g = 540 cal

Since this heat is taken away from the remaining water in the puddle, the temperature change can be calculated using the formula: 
Q = mcΔT 
where Q is the heat lost by the water, m is the mass of the water, c is the specific heat of water, and ΔT is the temperature change.

Solving for ΔT: 
ΔT = Q / (mc) 
where m = 190 g (mass of water in the puddle), c = 1 cal/g°C (specific heat of water)

ΔT = 540 cal / (190 g x 1 cal/g°C) 
ΔT = 2.84°C

Since 1 g of water has evaporated, the remaining mass of water in the puddle is 189 g. Therefore, the temperature change of the remaining water will be approximately -2.84°C (a decrease in temperature).

The closest answer choice is B) -2.8°C.

A Puddle Holds 190 G of Water