# Boyle's Law Explained

Boyle's Law provides an important formula to calculate the effect of changing pressure on the volume of a gas, and vice versa. It was put forward by a physicist Robert Boyle in the 17th century, and has proved very beneficial for scientists involved in the study of properties of gases.

Swapnil Srivastava

Last Updated: Feb 21, 2018

**About Robert Boyle**

Robert Boyle was born on January 25, 1627, and is considered as one of the founders of modern chemistry. Most of his research was carried out while he was in Oxford, and it mostly dealt with the behavior of gases. Besides science, Boyle was also interested in theology and learned various languages like Greek, Hebrew, and Syriac, in order to enhance his understanding of the scriptures. He also founded 'Boyle Lectures' to defend Christianity against other religions.

**Boyle's Law and its Mathematical Interpretation**

Boyle's Law helps to determine the effect on the volume of a gas by changing the pressure applied on it. The amount of gas and temperature should be kept constant, while performing the experiment in order to plot the correct relation between pressure and volume. The law states that if the temperature is kept constant, volume of a gas is inversely proportional to the pressure applied. Mathematically, the law can be represented as:

**PV = k**

where,

P = pressure of the system

V = volume of gas

k = a constant value

**P**

_{1}V_{1}= P_{2}V_{2}where P

_{1}and V

_{1}refer to the initial pressure and volume of the gas, and P

_{2}and V

_{2}denote the final pressure and volume of the gas. According to this equation, it can be easily concluded that if pressure applied on a gas is increased, its volume decreases, and similarly, if pressure is decreased, the volume increases in order to keep the value of 'k' constant. Boyle's Law was derived from the kinetic theory of gases, assuming an ideal gas. It was also discovered that real gases obey Boyle's Law only at a sufficiently low pressure, as at higher pressures, gases generally show deviation from their ideal behavior.

*Example*: Suppose the initial volume and pressure of the gas is 3 L and 4 atm, respectively, then using Boyle's law, the final pressure of gas can be calculated if the volume is decreased to 2.5 L.

**Solution:**

According to Boyle's law,

**P**

_{1}V_{1}= P_{2}V_{2}Therefore,

**P**

_{2}= (P_{1}V_{1}) ÷ V_{2}**P**

_{2}= (3 × 4) / 2.5 = 4.8 atm.Hence, the final pressure of the gas is 4.8 atm.