Question

PLEASE HELP WITH THESE TWO QUESTIONS

2.) 50.0 grams of water at 100 degrees Celsius evaporated to water vapor 2 points
at 100 degrees Celsius. Calculate the amount of heat required for this
conversion.

2. A student measured 15.0 grams of ice in a beaker. The beaker was then
placed on a hot plate where it was heated uniformly for a certain amount
of time. During the melting process of the ice, the student noted that the
temperature was at 0 degree Celsius. When all the ice converted to water,
the final temperature was also at 0 degree Celsius. How much heat was
used to melt the ice?

Answer 1

1. Q=112.8 kJ

2. Q=5.01 kJ

Further explanation

The heat required for phase change :

• melting/freezing :

Q = mLf

Lf=latent heat of fusion

• vaporization/condensation

Q = mLv

Lv=latent heat of vaporization

1.

m=50 g=0.05 kg

Lv (water) = 2256 kJ/kg

`\tt Q=0.05* 2256=112.8~kJ`

2.

m=15 g=0.015 kg

Lf for water = 334 kj/kg

`\tt Q=0.015* 334=5.01~kJ`