Question

A pure compound contains 2.4g of C, 1.2 × 10²³ atoms of H, 0.2 moles of oxygen atoms. Its empirical formula is

• A. C₂HO
• B. C₂H₂O₂
• C. CH₂O
• D. CHO

Answer 1

The Correct Option is D

Given:
Mass of Carbon (C) = 2.4 g
Number of hydrogen atoms = \(1.2 \times 10^{23}\) atoms
Moles of Oxygen (O) = 0.2 moles

Step 1: Calculate the number of moles of each element.

Carbon (C):
Molar mass of carbon = 12 g/mol.
Number of moles of carbon = \[ \frac{2.4 \, \text{g}}{12 \, \text{g/mol}} = 0.2 \, \text{moles of C} \]
Hydrogen (H):
The number of hydrogen atoms is \(1.2 \times 10^{23}\).
Molar mass of hydrogen = 1 g/mol.
Number of moles of hydrogen = \[ \frac{1.2 \times 10^{23}}{6.022 \times 10^{23}} = 0.2 \, \text{moles of H} \]
Oxygen (O):
Number of moles of oxygen = 0.2 moles.

Step 2: Find the ratio of moles of elements.
The ratio of moles of C : H : O = 1 : 1 : 1.

Step 3: The empirical formula is CHO.

The correct answer is (D) : CHO.

Answer 2

1. Moles of each element:

- C: $2.4 \, \text{g} / 12 \, \text{g/mol} = 0.2 \, \text{mol}$

- H: $(1.2 \times 10^{23} \, \text{atoms}) / (6.022 \times 10^{23} \, \text{atoms/mol}) \approx 0.2 \, \text{mol}$

- O: $0.2 \, \text{mol}$

2. Mole Ratio:

- C : H : O = $0.2 : 0.2 : 0.2$

3. Simplest Whole Number Ratio:

- Divide by $0.2 \, \text{mol}$ -> $1 : 1 : 1$

4. Empirical Formula:

- CHO