2.0 g of a bromo hydrocarbon (X) was subjected to Carius analysis, gave 3.36 g of AgBr. The percentage of carbon in the compound (X) is 26.7%. Total number of carbon atoms in the empirical formula for compound (X) is . (Given molar mass in g mol-1 H : 1, C : 12, Br : 80, Ag : 108)
Answer
5
Solution
Molar mass of AgBr = 108 + 80 = 188 g mol-1
% Br = 80188 3.362.0 100 = 71.5\%
X contains only C, H and Br ⇒ % H = 100 − 26.7 − 71.5 = 1.8%
Atom ratio C : H : Br = 26.712 : 1.81 : 71.580
= 2.225 : 1.8 : 0.894
Dividing by 0.894 ⇒ 2.49 : 2.01 : 1 ≈ 2.5 : 2 : 1
Multiplying by 2 ⇒ 5 : 4 : 2 ⇒ empirical formula C5H4Br2
∴ Number of C atoms = 5
Answer: 5