14.4 g sample of liquid ammonia is heated at a constant pressure of 1 atm from a temperature of 239.8 K to a temperature of 324.9 K. How much energy in kJ is required?
1 Answer
You must supply 10.59 kJ.
Explanation:
Here is a schematic heating curve for ammonia.
The boiling point of ammonia is 239.8 K (-33.4 °C).
Thus, you are starting with liquid ammonia at Point B on the graph, heating the liquid at its boiling point until it has wholly vaporized at Point C, and then heating the vapour until the temperature reaches 324.9 K (51.8 °C) at Point D.
There are two separate heat inputs involved in this problem:
#q_1# = heat added to vaporize the ammonia at 239.8 K#q_2# = energy added to heat the vapour from 239.8 K to 324.9 K
where
You must supply 10.59 kJ.