Find Oxygen Percentage from Combustion Analysis

❓ Question

Complete combustion of:

$$1.80\text{ g}$$

of an oxygen containing compound

$$(C_xH_yO_z)$$

gave:

$$2.64\text{ g of }CO_2$$

and

$$1.08\text{ g of }H_2O$$

The percentage of oxygen in the organic compound is ______.

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🖼 Question Image

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✍️ Short Explanation

This is a combustion analysis problem.

👉 Carbon comes from $CO_2$
👉 Hydrogen comes from $H_2O$
👉 Remaining mass belongs to oxygen.

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🔷 Step 1 — Mass of Carbon 💯

From:

$$CO_2$$

Molar mass:

$$44$$

Carbon present:

$$12$$

So carbon mass from:

$$2.64\text{ g }CO_2$$

is:

$$\frac{12}{44}\times2.64$$
$$=0.72\text{ g}$$

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🔷 Step 2 — Mass of Hydrogen

From:

$$H_2O$$

Molar mass:

$$18$$

Hydrogen present:

$$2$$

So hydrogen mass from:

$$1.08\text{ g }H_2O$$

is:

$$\frac{2}{18}\times1.08$$
$$=0.12\text{ g}$$

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🔷 Step 3 — Mass of Oxygen in Compound

Total compound mass:

$$1.80\text{ g}$$

So oxygen mass:

$$=1.80-(0.72+0.12)$$
$$=1.80-0.84$$
$$=0.96\text{ g}$$

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🔷 Step 4 — Percentage of Oxygen

$$\%\text{ Oxygen} = \frac{0.96}{1.80}\times100$$
$$=53.33\%$$

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🔷 Step 5 — JEE Trap Alert 🚨

❌ Direct $CO_2$ mass ko carbon mass maan lena

❌ Water se oxygen nikalna start kar dena

❌ Remaining mass concept bhool jaana

Remember:

$$\text{Oxygen mass} = \text{Total mass}-\text{(C + H mass)}$$

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✅ Final Answer

$$\boxed{53.33\%}$$

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