Question

Q3. The evaporation of water is monitored over time giving the following data: time / min 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 Vol. H20/1 0.250 0.248 0.247 0.245 0.244 0.242 0.240 0.239 0.237 0.236 0.234 0.233 0.231 0.229 0.228 0.226 0.224 0.223 0.221 0.220 0.218 0.217 0.215 0.213 0.212 0.210 (a). Based on this data, what can you say about the order of evaporation water with respect to its volume? (b). Under these conditions, how long would it take for the water to completely evaporate? (c). What might happen if the temperature of the water is raised with all other conditions kept constant? Explain your answer in terms of the kinetics and thermodynamics of evaporation.

This was the question i was given by my chem lecturer. Not sure how the data could be wrong?

Answer 1

(a)Based on the data, we can say that the rate of evaporation is independent of volume of water taken because you can see here that in every 2 sec the amount of water evaporated is equal i.e.0.002 l . So the rate is 0.001l / sec or 1ml/sec.

(b)since the rate of evaporation is 1 ml per sec and we have 250 ml oh water .so it will take 250 sec (as we have constant rate of evaporation) i.e. 4 minutes and 10 seconds.

(C)If temperature of water is raised then kinetic energy of molecules of water will increase .They will start vibration at higher frequency which will break the hydrogen bond and vanderwaals forces present between water molecules so all these molecule will start moving away from each other at higher rate leading to increase in rate of evaporation.