Question

A 4.44 L container holds 15.4 g of oxygen at 22.55°C. What is the pressure?

Answer 1

We use the Ideal Gas Equation to get...........`P=2.63*atm`

Explanation:

`P=(nRT)/V=((15.4*g)/(32.00*g*mol^-1)xx0.0821*(L*atm)/(K*mol)xx295.7*K)/(4.44*L)=`

`2.63*atm`.

Do the units cancel out to give an answer in `atm`? Do they? Don't assume that I haven't made a mistake!

How did I do this? Well for (i) I know that oxygen is a binuclear gas, i.e. `O_2`; in fact all the elemental gases (save for the Noble Gases) are BINUCLEAR.....and thus I used a molecular mass of `32.00*g*mol^-1` for dioxygen gas.......

And (ii) I knew the gas constant was............... `0.0821*L*atm*K^-1*mol^-1`.

And (iii) I knew the relationship between `""^@C` and `"degrees Kelvin"`.

These data (well (ii) and (iii)) need not be remembered, as they should be provided (with various units) in a chemistry exam. You still need to know how to use the appropriate gas constant, `R`.