Advertisements
Advertisements
Question
A metal M forms a volatile chloride containing 65.5% chlorine. If the density of the chloride relative to hydrogen is 162.5, find the molecular formula of the chloride (M = 56).
Solution
% age of M in the chloride = 100 − 65.5 = 34.5
| Element | Mass % age | Atomic mass | Rel. number of atoms | Simplest ratio |
| M | 34.5 | 56 | `34.5/56` = 0.6 | `0.61/0.61` = 1 |
| Cl | 65.5 | 35.5 | `65.5/35.5` = 1.84 | `18.4/0.6` = 3 |
The empirical formula of chloride = MCl3
The empirical formula of mass = 56 + 35.5 × 3
= 162.5 g
Vapour density = 162.5
Molecular density = 2 × vapour density
= 2 × 162.5
= 325.0 g
Molecular Formula = (Empirical formula) × n
and n = `"Molecular mass"/"Empirical formula mass"`
= `325.0/162.5`
= 2
∴ Molecular Formula = (MCl3)2 or M2Cl6
APPEARS IN
RELATED QUESTIONS
A compound has the following percentage composition by mass: carbon 14.4%, hydrogen 1.2% and chlorine 84.5%. The relative molecular mass of this compound is 168, so what is its molecular formula?
A compound made up of two elements X and Y has an empirical formula X2Y. if the atomic weight of X is 10 and that Y is 5 and the compound has a vapour density (V.D.) 25, find its molecular formula.
If the empirical formula of two compounds is CH and their vapour densities are 13 to 39 respectively, find their molecular formula.
A hydrocarbon contains 4.8g of carbon per gram of hydrogen. Calculate Find molecular formula, if its vapour density is 29.
Barium chloride crystals contain 14.8% water of crystallization. Find the number of molecules of water of crystallization per molecule.
A compound has O = 61.32%, S = 11.15%, H = 4.88% and Zn = 22.65%. The relative molecular mass of the compound is 287 amu. Find the molecular formula of the compound, assuming that all the hydrogen is present as a water of crystallization.
112 cm3 of a gaseous fluoride of phosphorus has a mass of 0.63 g. Calculate the relative molecular mass of the fluoride. If the molecule of the fluoride contains only one atom of phosphorus, then determine the formula of the phosphorus fluoride. [ F = 19, P = 31].
A compound X consists of 4.8% carbon and 95.2% bromine by mass. If the vapour density of the compound is 252, what is the molecular formula of the compound?
On analysis, a substance was found to contain:
C = 54.54%, H = 9.09%, O = 36.36%
The vapour density of the substance is 44, calculate its molecular formula.
An organic compound, whose vapour density is 45, has the following percentage composition,
H = 2.22%, O = 71.19% and remaining carbon. Calculate its molecular formula.
