Question

Elemental analysis is performed on an unknown organic substance which is found to contain 6 grams of hydrogen and 36 grams of carbon. What is the empirical formula for this unknown?
Group of answer choices

CH4

CH2

CH3

CH

Answer 1

To determine the empirical formula of the unknown organic substance, we first need to find the number of moles of carbon and hydrogen present in the sample.

1. **Calculate moles of carbon (C)**:
- Atomic mass of carbon = 12 g/mol
- Mass of carbon = 36 g
- Moles of carbon = mass / molar mass = 36 g / 12 g/mol = 3 moles

2. **Calculate moles of hydrogen (H)**:
- Atomic mass of hydrogen = 1 g/mol
- Mass of hydrogen = 6 g
- Moles of hydrogen = mass / molar mass = 6 g / 1 g/mol = 6 moles

3. **Find the simplest mole ratio**:
- The ratio of carbon to hydrogen is 3 moles C to 6 moles H.
- To simplify, divide both values by the smaller number of moles (which is 3):
- C: 3/3 = 1
- H: 6/3 = 2

4. **Write the empirical formula**:
- The empirical formula based on the simplest ratio is \( \text{CH}_2 \).

Thus, the empirical formula for this unknown substance is **CH2**.