Q. Find the number of moles of molecules present in 50 mL of an ideal gas exerting a pressure of 770 mm at 25 0 . ( R = 0.082 L atm mol -1 K-1 ).
Answer :
Given , volume of gas (V) = 50 mL = 0.05 L
Pressure of gas (P ) = 770 mm = 1.01 atm
Temperature ( T) = 250 C = ( 25 + 273) = 298 K
Universal gas constant ( R ) = 0.082 L atm mol-1 K-1
No of moles (n) = ?
Now again we know that ,
PV = nRT
n = PV / RT
n = (1.01 * 0.05 ) / (0.082 * 298 ) = 2.066 * 10 -4 mol
Hence , number of moles of the gas is 2.066 * 10 -4 mol.