Air contains 21% of oxygen by weight. What weight of air is required to burn 50 grams of coal which contains only 50% combustible material?

see full answer

Talk to JEE/NEET 2025 Toppers - Learn What Actually Works!

Real Strategies. Real People. Real Success Stories - Just 1 call away

An Intiative by Sri Chaitanya

634 g

200 g

317 g

158.5 g

answer is A.

(Unlock A.I Detailed Solution for FREE)

Ready to Test Your Skills?

Check your Performance Today with our Free Mock Test used by Toppers!

Take Free Test

Detailed Solution

weight of coal = 50grams
percentage of Combustible material in coal = 50%
$weight\;of\;combustible\;material\;in\;coal\;=\;\frac{50}{100}\times 50=25g$

$\large \mathop C\limits_{25g}^{12g} \; + \;\mathop {{O_2}}\limits_{'X'g}^{32g} \; \to C{O_2}$

$\large X\; = \;\frac{{25\; \times \;32}}{{12}}g$
$\large weight\;of\;oxygen\;in\;air\;=\left ( \frac{25\times 32}{12} \right )g$
weight % of oxygen in air = 21%
$\large weight\;of\;air\;required\;=\left ( \frac{25\times 32}{12}{\times \frac{100}{21}} \right )g$
weight of air required = 317g