Translate the following statement into chemical equation and balance it: Hydrogen gas combines with nitrogen to form ammonia.

A balanced equation is an equation for a chemical reaction in which the number of atoms for each element in the reaction and the total charges is the same for both the reactants and the products. The balanced chemical equation for the reaction of hydrogen with nitrogen to form ammonia is: 3 H 2 g + N 2 g → 2 NH 3 g

Define exothermic reactions. Give any two examples.

The chemical reactions in which heat is released to its surroundings are called exothermic reactions. These reactions are accompanied by an increase in the temperature of the reaction mixture. The opposite of exothermic reactions is endothermic reactions, in which heat is absorbed. Two examples of exothermic reactions are: (i) When carbon burns in oxygen to form carbon dioxide, a lot of heat is produced. C + O 2 → CO 2 + heat (ii) When water is added to quicklime, slaked lime is produced along with a large amount of heat. CaO + H 2 O → Ca ( OH ) 2 + Heat

State any two conditions required for combustion.

Two conditions required for combustion are: 1. There must be fuel to burn. 2. There must be air to supply oxygen. In addition to these, there must be heat(ignition temperature) to start and continue the combustion process.

A catalyst is an agent that alters the rate of a chemical reaction without undergoing any permanent chemical change in the reaction. For example, nickel, platinum or palladium is used as a catalyst in the hydrogenation reaction of unsaturated compounds.