Question

During the dissolution of urea, heat:
A. is absorbed
B. is evolved
C. does not change
D. none of the above

Answer 1

Hint: To solve this question, we must first understand what is dissolution of urea. Then we need to assess the process of dissolution of urea and the heat energy involved in the process and then only we can conclude the correct answer.

Complete step by step solution:
Before we move forward with the solution of this given question, let us first understand some basic concepts:
Urea which is also known as carbamide, is an organic compound with chemical formula $ CO{(N{H_2})_2} $ . And the amide here has two $ - N{H_2} $ groups joined by a carbonyl $ (C = O) $ functional group. Urea plays an important role in the metabolism of nitrogen-containing compounds by animals. It is the main nitrogen-containing substance in the urine of mammals. Urea is a colorless and odorless solid, highly soluble in water, and non-toxic in nature. It is neither acidic nor basic.
Now, let’s discuss the dissolution of urea:
Dissolution refers to a solute dissolving in a solvent to form a solution. And in this experiment the solute is urea (solid). Urea is a molecular compound, so it does not dissociate into ions. The dissolution process involves energy to break the attractive bonds and forces between the molecules in the compound and releasing energy as the molecules form new attractive forces with the water molecules. And therefore, during the dissolution of urea a definite amount of heat is absorbed because dissolution is an endothermic reaction.
Therefore the correct answer is Option A.

Note:
 Urea is a raw material for the manufacture of two materials: urea-formaldehyde resins and urea-melamine-formaldehyde used in marine plywood. Urea is widely used to make urea nitrate, which is a highly explosive that is used in industrial and it is a part of some improvised explosive devices. It is a stabilizer in nitrocellulose explosives.