0.070g of hydride of carbon occupies 56cm^3 at S. T. P when vaporized and contained 14.29% by mass of hydrogen. What is the formula for the hydrocarbon

C₂H₄

Step-by-step explanation:

Assume that you have 100 g of the compound.

Then you have 85.71 g of C and 14.29 g of H.

1. Calculate the moles of each element.

Moles of C = 85.71 * 1/12.01 = 7.130 mol C

Moles of H = 14.29 * 1/1.008 = 14.18 mol H

2. Calculate the molar ratios.

Divide all values by the smallest number.

C: 7.130/7.130 = 1

H: 14.18/7.130 = 1.986

3. Determine the empirical formula

Round off all numbers to the closest integer.

C: 1

H: 2

The empirical formula (EF) is CH₂.

4. Calculate the EF mass

EF Mass = (12.01 + 2.016) u

EF Mass = 14.03 u

5. Calculate the moles of compound

STP is 0 °C and 1 bar.

1 mol of a gas occupies 22.71 dm³ at STP.

56 cm³ = 0.056 dm³ Convert to moles

= 0.056 * 1/22.71

= 2.47 * 10⁻³ mol

6. Calculate the molar mass

MM = mass/moles

= 0.070 g/2.47 * 10⁻³ mol

= 28.39 g/mol

7. Calculate the molecular formula (MF)

The molecular formula is an integral multiple of the empirical formula.

MF = (EF) ₙ

n = MF Mass/EF Mass

= 28.39 u/14.03 u

= 2.023

≈ 2

MF = (CH₂) ₂

= C₂H₄

The molecular formula is C₂H₄.