Question

The density of alcohol is $780{\text{kg/m}}^3$. Its relative density is

• A. $7.8{\text{g/cm}}^3$
• B. $7.8$
• C. $7.8{\text{kg/m}}^3$
• D. $0.78$

Answer 1

The correct option is B $7.8$

Given that, density of alcohol$=780{\text{kg/m}}^3$
We have,
Relative density $=\frac{{\rho }_{\text{alcohol}}}{{\rho }_{\text{water}}}$
In SI unit, ${\rho }_{\text{water}}=1000{\text{kg/m}}^3$
Thus, relative density$=\frac{{\rho }_{\text{alcohol}}}{{\rho }_{\text{water}}}=\frac{780}{1000}=0.78$