Oxygen is present in a 1 litre flask at a pressure of 7.6 xx 10^(-10) mm of Hg. Calculate the number of oxygen molecules in the flask at 0^@C

Oxygen is present in a 1 litre flask at a pressure of 7.6 xx 10^(-10)

1.	Oxygen is present in a 1 litre flask at a pressure of 7.6 xx 10^(-10) mm of Hg. Calculate the number of oxygen molecules in the flask at 0^@C
Answer» Solution :According to the ideal gas equation, PV = nRT In the present case, `P= 7.6 XX 10^(-10)mm = (7.6xx10(-10))/760 = 1.0xx10^(-12)` atm ( `:. 1 " atm " = 760 mm Hg)` `V = 1 L, and T = 0^@C = 273 K, " and "R=0.0821 " litre atm " K_(-1) mol^(-1)` `:.n=(PV)/(RT)= (1.0 xx 10^(-12) xx1)/(0.0821 xx 273) = 4.5 xx 10^(-14)` moles `:. " 1 mole " = 6.022 xx 10^(23)` molecules `:.4.5 xx 10(-14) " moles "= 6.022 xx 10^(23) xx 4.5 xx 10^(-14) = 2.7 xx 10^(10)`molecules Hence, the number of molecules of OXYGEN present in the flask at `0^@C " are " 2.7 xx 10^(10)` .