Boyle’s Law - Practice Questions & MCQ

An Anglo-Irish scientist 'Robert Boyle' in 1662 gave the pressure-volume relationship of a gas. He made some experiments on the basis of which he concluded that  "At constant temperature, the pressure of a fixed amount of gas varies inversely with the volume of the gas." That means if the pressure is doubled, the volume is halved.

k₁ is the proportionality constant whose value depends upon the following factors.

1. Amount of gas

2. Temperature

On rearranging the above equation we can write

i.e., 'PV' is constant at constant temperature and for a fixed amount of the gas. So, Boyle's law can also be stated as "At constant temperature, the product of pressure and volume of a fixed amount of a gas remains constant."
Now if the initial pressure and volume of a fixed amount of gas at constant temperature are P₁ and V₁, and after expansion, the new pressure of the gas is P₂ and volume occupied is V₂ then according to Boyle's law

Relation between Density and Pressure

Various plots between P vs V 
These plots are called Isotherms.

                       

Physical Significance of Boyle's Law : 
As discussed before, on increasing pressure, the density of the air increases at constant temperature. This indicates that gases are compressible. Same effect can be seen in daily life. Air is denser at the sea level and as the altitude increases air pressure decreases, which means air now becomes less denser. So, less oxygen molecules occupy the same volume. Therefore oxygen in air becomes insufficient for normal breathing, out of the result altitude sickness occurs with symptoms like headache, uneasiness. That is why mountaineers have to carry oxygen cylinders with them in case of emergency to restore normal breathing.