The 0.2 g of anhydrous organic acid gave on combustion 0.04g of water and 0.195 g of CO2. The acid is a dibasic acid and 0.5 g of its silver salt leaves on ignition 0.355 g of silver. The empirical weight of the compound is
(A) 90
(B) 100
(C) 10
(D) 45
Answers
The empirical weight of the compound is (COOH)₂
Explanation:
R(COOAg)₂ → Ag + R(COO⁻)₂
0.5 g → 0.355 g + 0.145 g
Number of moles of Ag is:
⇒ 0.355/108
Number of moles of R(COO⁻)₂ is:
⇒ 0.355/216
Molecular weight of R(COO⁻)₂ is:
⇒ 0.145/(0.355/216) = 88
Molecular weight of R(COOH)₂ is:
⇒ 88 + 2 = 90
From question, number of moles in 0.2 g of anhydrous organic acid is:
⇒ 0.2/90= 0.002222 moles
From question, number of hydrogen moles in 0.04 g of water is:
⇒ 0.04 × 2/18 = 0.004444 moles
From question, number of carbon moles in 0.195 g of CO₂ is:
⇒ 0.195/44 = 0.00444 moles
Thus, in 1 mole of acid, we get 2 moles of hydrogen and 2 moles of carbon.
The molecular formula of acid is (COOH)₂
The correct option is D(45)
The empirical formula of the compound is cho2 (molecular formula is (cho2)2)
The empirical weight is 12+1+2(16)=45
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