What is the molar mass of the gas?

A sample of a gas weighs 4.126g and has a volume of of 1020.0 mL at 775.0 torr and 24.0 C. What is molar mass?

• What is its molar mass?

• Answer:

  You have to use the Ideal Gas Law equation, PV=nRT where P is pressure in atmospheres, V is volume in Liters, n is moles of gas, n is the universal gas constant which is .0821, and T is temperature in Kelvins. First, convert all of the units in the problem to desired units in the equation. First, mL to L. There are 1000 mL per Liter, so 1020ml=1020e-3L. Carry the decimal and it is 1.020 L. Next, the pressure. There are 760 torr in one atmosphere. So, 775.0/760 is our pressure. Finally, temperature. To get to Kelvin, just add 273 to Celsium. 24+273=297 K. Now, use the equation: (775/760)(1.020)=n(.0821)(297) ((775/760)(1.020))/((.0821)(297))=n Moles (n) = grams of the substance per molar mass, or written as n=g/MM Therefore, substitute your answer from the first part for moles for the n in this new equation. Grams is given in the problem, 4.126, so just solve with algebra. I will substitute in the numbers but not solve the equation: ((775/760)(1.020))/((.0821)(297))=4.12… 4.126/((775/760)(1.020))/((.0821)(297)…