Question

8.0 g of a monoatomic gas occupies 96.0 L at 380.9 mm Hg and 20.0 °C. What is the identity of the gas?

Answer 1

The monoatomic gas : He

Further explanation

In general, the gas equation can be written

`\large {\boxed {\bold {PV = nRT}}}`

where

P = pressure, atm

V = volume, liter

n = number of moles

R = gas constant = 0.08206 L.atm / mol K

T = temperature, Kelvin

P 380.9 mmHg = 0.5 atm

T 20 C+273 = 293 K

We can find molar mass of gas :

`\tt M(molar~mass(M)=(mRT)/(PV)\\\\M=(8~g* 0.082* 293~K)/(0.5~atm* 96~L)\\\\M=4~g/mol`

monatomic gas means a single element, usually a noble gas. The noble gas element with mass 4 is He