an equimolar mixture of n2(g)n2(g) and ar(g)ar(g) is kept inside a rigid container at a constant temperature of 300 kk. the initial partial pressure of arar in the mixture is 0.75atm0.75atm. an additional amount of arar was added to the container, enough to double the number of moles of arar gas in the mixture. assuming ideal behavior, what is the final pressure of the gas mixture after the addition of the arar gas?