I hate stoichiometry. I will help you but I need to know the question first.
Answer : The volume of oxygen at STP is 112.0665 L
Solution : Given,
The number of moles of
= 5 moles
At STP, the temperature is 273 K and pressure is 1 atm.
Using ideal gas law equation :

where,
P = pressure of gas
V = volume of gas
n = the number of moles
T = temperature of gas
R = gas constant = 0.0821 L atm/mole K (Given)
By rearranging the above ideal gas law equation, we get

Now put all the given values in this expression, we get the value of volume.

Therefore, the volume of oxygen at STP is 112.0665 L
The salt causes the water to freeze at a lower temperature. When a solute, aka salt, is introduced to the system, the freezing point is lowered. This makes the water freeze at a lower temperature.