need help working out this problem

Question

What is the mass of neon that exerts a pressure of 720. mmHg,with a temperature of -15.0 °C , when the volume of the container is 760. mL?

 

A) 0.0340 g B) 0.686 g C) 0.615 g D) 517 g E) 25.8 g

Answer 1

Use the ideal gas law to calculate the amount (moles) of Ne and the convert moles to mass. Ideal gas law is:

 

PV = nRT

 

Pressure (P) =720 mmHg

Volume (V)=760 mL= 0.760 L

Temperature (T)=-15ºC = 258 K

moles (n) = unknown

Universal gas constant (R)= 62.4 (L·atm)/(mol·K)

 

Find the number of moles (n):

 

n=PV/RT=(720 mmHg)(0.760L)/(62.4 L·atm/mol·K)(258 K)=0.0340 mol Ne

 

Use the molar mass as a conversion factor to calculate the mass of Ne:

 

0.0340 mol Ne × 20.18 g Ne/(1 mol Ne) = 0.686 g Ne

 

Your answer choice is B, 0.686 g Ne