1. A volume of 18.0 L contains a mixture of 0.250 mole N2 , 0.250 mole O2 , and an unknown quantity of He . The temperature of the mixture is 0 ∘C , and the total pressure is 1.00 atm . How many grams of helium are present in the gas mixture?

2. A gas sample has a unknown pressure with a temperature of 51 ∘C . The same gas has a pressure of 2.96 atm when the temperature is -50. ∘C , with no change in the volume or amount of gas. What was the initial pressure, in atmospheres, of the gas?

2b.How many grams of NO2 will be produced when 2.1 L of nitrogen at 820 mmHg and 25 ∘C are completely reacted? 2c.What volume of O2 at 760. mmHg and 31 ∘C is required to synthesize 21.5 mol of NO ?