5dm3 of dry oxygen gas is allowed to expand to 7dm3, when its pressure recorded is 700mm of Hg. Find?initial pressure of gas, assume temperature remain constant. ? ?[980mm of Hg].

Dear Student,
According to the gas equation,


Given that V₁ = 5dm³,
                  V₂ = 7dm³
  (final pressure)  P₂ = 700mm of hg,
 As t​​​​​​he temperature is constant,so the equation will be P₁V₁ = P₂V₂
to find : P₁ (initial pressure) = ?
Putting all the values in the above equation,we get
P₁ $\times$ 5 = 700 $\times$7
P₁  = 980 mm of hg (initial pressure of gas)
Regards