A gas is contained in a closed vessel .How pressure due to the gas will be affected if force of attraction between the molecules disappear suddenly?

As force of attraction between molecules disappears, then molecules will hit the wall with more speeds, hence, rate of change of momentum will increase. As we know F = ∆p / ∆t, where F is average force on the wall due to molecules. ∆p is change in momentum and At is the time duration. Due to increase in ∆p force F will also increase, hence F . . .

pressure p = F/A will increase. Here, A is area of one wall.