Question

Sodium chloride (NaCl) reacts with silver nitrate ($AgN{O_3}$) to produce silver chloride (AgCl) and sodium nitrate ($NaN{O_3}$). The law which satisfies the equation is:
(A) Conservation of mass
(B) Conservation of energy
(C) Newton’s law
(D) Dalton’s law

Answer 1

Hint: In any reaction, the total mass remains constant unless the substance undergoes radioactive decay. If the substance is radioactive, then energy and mass are related as $E = m{c^2}$.

Complete step by step answer:
The reaction of sodium chloride with silver nitrate is given below:
$NaCl + AgN{O_3} \to AgCl + NaN{O_3}$
The above reaction is a balanced reaction. Therefore, the reactants can react in the stoichiometric ratios to give products in their respective stoichiometric ratios. So, one mole of NaCl reacts with one mole of $AgN{O_3}$ to produce one mole of AgCl and $NaN{O_3}$ each. AgCl is precipitated at the bottom of the beaker.
Now, we know the individual masses of the constituents of the reaction.
Mass of Na = 23u
Mass of Cl = 35.5u
Mass of Ag = 107.8u
Mass of N = 14u
Mass of O = 16u
Therefore, mass of NaCl = 23u + 35.5u = 58.5u
Mass of $AgN{O_3}$ = 107.8u + 14u + 3(16)u = 169.8u
So, mass of reactants = 228.3u
And, mass of AgCl = 107.8u + 35.5u = 143.3u
Mass of $NaN{O_3}$ = [23 + 14 + 3(16)]u = 85u
So, mass of products = 143.3u + 85u = 228.3u
Hence, the mass is conserved in the reaction.
Therefore, the correct answer is (A) Conservation of mass.

Note: Law of conservation of mass states that in a chemical reaction, mass can neither be created nor be destroyed. Make sure to remember, it is applicable unless the reaction does not undergo radioactive changes.