A compound has an empirical formula of CH_2 and a relative molecular mass of 42. What is t… — JAMB UTME

A compound has an empirical formula of $CH_2$ and a relative molecular mass of $42$ . What is the molecular formula of the compound? $[C = 12, H = 1]$

$C_3H_6$ Answer
B
$C_2H_4$
C
$C_4H_8$
D
$CH_2$

Answer

The molecular formula of the compound is

C_3H_6

The empirical formula mass of

CH_2

14\text{ g/mol}

. Dividing the given relative molecular mass (

42

) by

14

gives an integer factor

n = 3

. Multiplying the empirical formula indices by

3

gives

C_3H_6

Step-by-Step Solution

Calculate the empirical formula mass of

CH_2

Empirical formula mass

= 12 + 2(1) = 14\text{ g/mol}

The empirical formula mass is required to find the integer ratio multiplier

n

Determine the integer multiplier

n

by dividing the relative molecular mass by the empirical formula mass.

n = \frac{42}{14} = 3

The integer multiplier indicates how many empirical units constitute the molecular formula.

Multiply the subscripts of the empirical formula

CH_2

n = 3

Molecular formula

= (CH_2)_3 = C_3H_6

Applying the integer multiplier yields the true formula of the compound.

Key Concept

Molecular Formula Derivation from Empirical Formula and Molar Mass

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