2.600g Cl2 and 1.800g H2 are placed in a 4.00L flask at 21.5 degrees C, what would be total pressure in flask?

Assuming this is an ideal gas, you can use the ideal gas law:
PV = nRT

P = nRT/V

R is a constant, T is given (make sure to convert to Kelvin), V is given.
You basically just need to find n - the number of moles. You are given the mass of each gas (m), and using the periodic table you can find the molar mass (M) in g/mol. Then find the moles using simply n = M/m. Do this for each gas and add the moles together.
After that you have everything to plug into the ideal gas formula and get the pressure.

ok thats what i was kind of wondering, if you just find the mols for each gas seperately, then add them together, or if you have to do a balanced equation then find the mols from there or what

Well, the question doesn't say whether the gasses react or not, but if they do you end up with the same number of moles anyway.

This post was edited by russian on Oct 27 2016 09:26am