Question

Take about 2 g barium hydroxide in a test tube. Add 1 g of ammonium chloride and mix with the help of a glass rod. Touch the bottom of the test tube with your palm. What do you feel? Is this an exothermic or endothermic reaction?
NCERT Class 10th Science Chapter 1 Chemical Reactions and Equations

Answer 1

The base of the test tube is cold. This shows us that the reaction of barium hydroxide with ammonium chloride is endothermic. We call it endothermic as heat is being absorbed in the reaction.

Answer 2

When the test tube is touched, it "feels cold".

Barium Hydroxide is a base whereas ammonium chloride is acidic in nature, thus this reaction is an endothermic reaction.

An endothermic reaction, the reaction that takes heat from its surroundings which is in fact essential for the reaction to take place. When the heat is absorbed it gives out coldness.

$\bold{\mathrm{B a(O H)_{2}+N H_{4} C l \rightarrow B a C l_{2}+N H_{3}+H_{2} O}}$