If relative molecular mass of butane (C₄H₁₀) is 58, then its vapour density will be:

1. 5

2. 29

3. 32

4. 16

29

Reason

Given relative molecular mass of (C₄H₁₀) is 58

2 x Relative V.D. = $\dfrac{\text{mass of 1 molecule of gas or vapour}}{\text{mass of one atom of hydrogen }}$

2 x Relative V.D = Relative molecular mass of a gas or vapour.

Rearranging the above formula

Relative V.D = $\dfrac{\text{Relative molecular mass of a gas or vapour}}{\text{2}}$

Relative V.D = $\dfrac{58}{2}$ = 29

Hence the vapour density of (C₄H₁₀) is 29