a compound has vapour density 45 and empirical formula is CHO2to find molecular formula
Answers
Answer:
The molecular formula is C6H6.
Explanation:
The chemical composition of a compound is given by the chemical formula. This formula can either be empirical formula or actual molecular formula. Empirical formula is the simplest formula of a compound which gives ratio of different atoms present in one molecule of the compound. On the other hand, the molecular formula gives actual number of atoms of each element present in one molecule of the compound. For example, hydrogen peroxide contains only hydrogen and oxygen. The simplest ratio is 1 : 1. Since, empirical formula is HO and empirical formula mass is 17. However, the actual hydrogen peroxide contains two atoms of hydrogen and two atoms of oxygen. Hence the molecular formula is (HO)2 = H2O2 and molecular mass is 34. Therefore, the molecular formula is twice the empirical formula.
Molecular formula = n Empirical Formula
For some molecules like C2H2, C6H6, the empirical formula is the same, i.e. CH. But the molecular formula is different.
Also, for molecules like CH4, CO, etc., both the empirical and molecular formulae are the source. Thus, molecular formula is either identical with the empirical formula or a simple multiple of it.
The empirical formula is calculated from percentage composition of each element present in the molecule. The molecular mass is calculated from vapour density and can be determined by various methods.
Molecular mass = 2 Vapour density
The actual molecular formula is calculated from empirical formula and the molecular mass.
Example: The vapour density of a compound having empirical formula CH is 39. Find its molecular formula.
Solution: Empirical formula = CH
Empirical formula mass = 12 1 + 1 1 = 13
Molecular mass = 2 vapour density
= 2 39
= 78
Molecular formula mass = n Empirical formula mass
=
= 6
Molecular formula = n Empirical formula
= 6 (CH)
= C6H6
The molecular formula is C6H6.
Answer:
C2H2O4
Explanation:
molecular mass = 2 * vapour density
therefore
molecular mass = 2*45=90
we know
molecular wt. = n* empirical wt.
n= molecular wt./empirical wt.
n = 90/12+1+16*2 = 2
molecular formula = n * empirical formula
molecular formula = 2 * CHO2 = C2H2O4