Advertisements
Advertisements
Question
Complete the following calculations. Show working for complete credit :
If the empirical formula of a compound is CH and it has a vapour density of 13, find the molecular formula of the compound.
Advertisements
Solution
For acetylene , molecular mass = 2 X V.D. = 2 x 13 = 26g
The empirical mass = 12 (c) + 1(H) = 13g
n = `"Molecular formula mass"/"Empirical formula weight"`
= `26/13` = 2
Molecular formula of acetylene = 2 x Empirical formula =C2H2
Similarly, for benzene molecular mass = 2 X V.D = 2 x 39 = 78
n = 78/13 = 6
So, the molecular formula = C6H6.
APPEARS IN
RELATED QUESTIONS
Define the term:
Vapour density
The usefulness of a fertilizer depends upon percentage of nitrogen present in it. Find which of the following is a better fertilizer:
(a) Ammonium nitrate [NH4NO3]
(b) Ammonium phosphate [(NH4)3PO4 (N=14,H=1,O=16,P=31)
Potassium nitrate on strong heating decomposes as under :
2KNO3 → 2KNO2 + O2
Calculate : Weight of oxygen formed when 5.05g of potassium nitrate decomposes completely.
(K = 39, 0 = 16, N = 14)
Calculate the percentage of water in ferrous sulphate crystals.
[Fe = 56, S = 32, O =16, H = 1].
If the relative molecular mass of A is 90, what is the molecular formula of A?
The reaction of potassium permanganate (VII) with acidified iron (II) sulphate is given below:
2KMno4 + 10FeSO4 + 8H2O → K2SO4 + 2MnSO4 + 5Fe2(SO4)3 + 8H2O
If 15.8g of potassium permanganate (VII) was used in the reaction, calculate the mass of iron (II) sulphate used in the above reaction.
What is the vapour density of ethylene? (Avogadro's number = 6 x 1023; Atomic weight of C = 12, H = 1; Molar volume = 22.4 litres at STP)
Give one word or phrase for the following:
Formation of ions from molecules.
Explain the term:
Vapour density
Calculate the relative molecular mass of:
(NH4)2SO4
