# Chemistry Class 11 NCERT Solutions: Chapter 1 Some Basic Concepts of Chemistry Part 4

Q: 13. Pressure is determined as force per unit area of the surface. The SI unit of pressure, Pascal is as shown below:

If mass of air at sea level is, calculate the pressure in Pascal.

Pressure is defined as force acting per unit, area of the surface.

We know,

Then,

Q: 14. What is the SI unit of mass? How is it defined?

The SI unit of mass is kilogram (kg). 1 kilogram is defined as the mass equal to the mass of the international prototype of kilogram.

Q: 15. Match the following prefixes with their multiples:

 Prefixes Multiples (i) micro Equation (ii) Deca Equation (iii) Mega Equation (iv) Giga Equation (v) Femto Equation