Question

Calculate the relative density of zinc when its density is $7g/{cm}^3$.

• A. $0.7$
  
• B. $3.5$
  
• C. $49$
  
• D. $7$
  

Answer 1

The correct option is D $7$

Relative density$\left({\rho }_o\right)$ is defined as the ratio of density of any substance to the density of water at $4^{\circ }C$.

The relative density of water at $4^{\circ }C$ is $1g/c{m}^3$.

${\rho }_o=\frac{Densityofsubstance}{Densityofwater}$

${\rho }_o=\frac{7g/c{m}^3}{1g/c{m}^3}$

Thus the magnitude of density of any substance is equal to the magnitude of its relative density. Thus the relative density is $7$ and since it is the ratio of two similar quantities it has no units.