Answer : The pressure of the gas is, 8.42 atm
Explanation :
Using ideal gas equation, 
 
where, 
P = pressure of the gas = ?
V = volume of the gas = 748 ml = 0.748 L
conversion used : (1 L = 1000 ml) 
T = temperature of the gas = 

n = number of moles of the gas = 0.255 mole
R = gas constant = 0.0821 L.atm/mole.K 
Now put all the given values in the ideal gas equation, we get the pressure of the gas.
 

Therefore, the pressure of the gas is, 8.42 atm