Question

one liter of gas at ntp weigh 1.97 calculate molecular mass

Answer 1

Assuming the gas to be ideal gas.

PV=nRT

PV=mRT/M

where m is mass of gas, M is molar mass

At NTP, T = 273K, P = 1atm

Therefore,
M = mRT/PV

M = 1.97*0.082*273/1*1

M = 44.1 g/mol