Question

Write the balanced equation for preparation of \[N{H_3}\] from ammonium chloride and calcium hydroxide.
A. \[4N{H_4}Cl + Ca{(OH)_2} \to 2N{H_3} + 2CaC{l_2} + 2{H_2}O\]
B. \[2N{H_4}Cl + 2Ca{(OH)_2} \to 2N{H_3} + 2CaC{l_2} + 2{H_2}O\]
C. \[2N{H_4}Cl + Ca{(OH)_2} \to 2N{H_3} + CaC{l_2} + 2{H_2}O\]
D. \[N{H_4}Cl + Ca{(OH)_2} \to N{H_3} + CaC{l_2} + 2{H_2}O\]

Answer 1

Hint: To balance the reaction, we can use the law of conservation of mass. Hit and trial method is used to balance the number of atoms on both, left and right side of the reaction. The mass of products in a chemical reaction must be equal to the mass of reactants.

Complete step by step answer:
-According to the law of conservation of mass, in an isolated system, mass is neither created nor destroyed by any chemical or physical transformations.
-A chemical equation represents the substances that are involved in a chemical reaction i.e. reactants and products. The balanced chemical equation is the one which has the same number of atoms on both sides of a reaction.
-When ammonium chloride reacts with slaked lime or calcium hydroxide, ammonia gas is evolved with its characteristic pungent odour. Calcium hydroxide is a stronger base and thus displaces ammonia which is a weaker base from the ammonium chloride salt. From this, we can draw a conclusion that any alkali can displace ammonia from ammonium salts.
-Along with ammonia, two more products are formed. These are calcium chloride and water molecules. Now we know the reactants used and products formed in this chemical reaction, so we can balance the chemical equation by counting and equalising the number of atoms of each species involved on both the sides of an arrow.
 \[2N{H_4}Cl + Ca{(OH)_2} \to 2N{H_3} + CaC{l_2} + 2{H_2}O\]

Type of Atom	No. of atoms on left side	No. of atoms on right side
N	2	2
Ca	1	1
O	2	2
H	10	10
Cl	2	2

Hence, the correct option is (C).

Note:
These balancing numbers are called stoichiometric coefficients. It is the number written in front of atoms, ions and molecules in a chemical reaction to balance the number of each element on both the sides. It gives the ratio of moles of reactants and products. It can be a fraction value too.