Name: An Introduction to Chemistry
Uploaded: 2019-07-19
Duration: 1 min 45 s
Description: Chemistry is the branch of science dealing with the structure, composition, properties, and reactive characteristics of matter. Let's explore the video to kn...

Question

$20 mL$ of a mixture of methane and a gaseous compound of Acetylene series were mixed with $100 mL$ of oxygen and exploded. The volume of the products after cooling to original room temperature and pressure, was $80 mL$ and on treatment with potash solution a further contracting of $40 mL$ . was observed. Calculate

(a) the molecular formula of the hydrocarbon,

(b) the percentage composition of the mixture.

Accepted Answer

$\underset{a}{{CH}_{4}} + \underset{2 a}{2 O_{2}} ⟶ \underset{a}{{CO}_{2}} + 2 H_{2} O$

$C_{n} H_{2 n - 2} + (\frac{3 n - 1}{2}) O_{2} ⟶ {nCO}_{2} + (n - 1) H_{2} O$

$(20 - a) (\frac{3 n - 1}{2}) (20 - a) n (20 - a)$

For methane $a + n (20 - a) = 40 . . . (1)$

For oxygen $[100 - 2 a - (\frac{3 n - 1}{2}) (20 - a)] = 40$

$2 a + (\frac{3 n - 1}{2}) (20 - a) = 60$

$2 a + 30 n - 1.5 na - 10 + 0.5 a = 60$

$2.5 a + 1.5 n (20 - a) = 70 . . . (2)$

from $(1) & (2)$

$a = 10$

$n = 3$

$C_{3} H_{4}$

$%$ composition= 10/20 X100 $= 50 %$

Important Questions on Some Basic Concepts of Chemistry

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