Question

An inorganic salt contains 15.89% calcium, 2.4% hydrogen, 24.6% phosphorus and
57.11% oxygen. Its molecular mass is 252.2. Deduce its molecular formula.​

Answer 1

Answer:

molecular formula is = Ca H₃ P₂ O₈

Explanation:

ELEMENT           % composition        at.wt       relative no. of atoms         ratio

CALCIUM               15.89                    40            15.89/40 = 0.39     0.39/0.39=1

HYDROGEN           2.4                        2              2.4/2 = 1.2              1.2/0.39 = 3

PHOSPHORUS        24.6                    31             24.6/31 = 0.79        0.79/0.39=2

OXYGEN                 57.11                     16             57.11/16 = 3.5          3.5/0.39=8

based on the above table, we get the empirical formula,  Ca H₃ P₂ O₈

molecular formula = n * empirical formula

n = given mass/calculated mass of the compound

n = 252.2/236 = 1 (approx)

so, molecular formula = n * empirical formula

which is 1 * Ca H₃ P₂ O₈ = Ca H₃ P₂ O₈