How to find pressure of an unknown gas?

Question

An unknown gas is placed in a cylinder that has a movable piston. The volume of the cylinder is set at 6.0 L and the resulting pressure is 735 mm Hg. The piston is pushed into the cylinder and the volume decreases to 4.7 L. What will the pressure be if the temperature was constant?

Answer 1

By Boyle's law, the product of the pressure and volume of an amount of gas are constant., if the temperature doesn't change.

 

In other words, P₁V₁ = P₂V₂

 

P₁V₁ = 735 * 6 = 4410

 

So P₂V₂ = 4410

 

We know that V₂ is 4.7 L, so that means that P₂ * 4.7 = 4410.

 

So P₂ = 4410 / 4.7 = 938.3 mm Hg.