HELP! I need help solving these chemistry questions before midnight! Please and thank you!

Question

a.A sealed container of an unknown gas has a volume of 2.5 L and a pressure of 5 atm at 25​o​C.How much gas is in the container?

b.If the mass of the gas in the container is 40.5 g, what is the identity of the gas?

c.In a complete sentence, explain how you determined the identity of the gas.

Answer 1

Part 1) Use this equation:

PV = nRT

where, P = pressure, V = Volume, n = moles of gas, R = ideal gas constant, T = Temperature (in degrees Kelvin)

Solve for n (how much gas is in the container)

n = PV/RT = (5 atm)(2.5 L)/(.082057)(298.15 K) = 0.51 moles of gas

note: I converted degrees Celsius to degrees kelvin by simply adding 273.15 to it.

notes: I used the ideal gas constant, R = .082057 L*atm/(mol*K) because it has the units of the other values in the question

Part 2) we must find the atomic mass to identify the element. We need g/mol.

40.5g/0.51moles = 79.4 g/mol (79 g/mol is our actual answer if we are paying attention to significant figures).

The element of Bromine has an atomic mass of 79.9 g/mol...this is the closest option.

3) I identified the gas in the container by dividing the known mass of my sample by the known amount of moles of my sample to obtain the atomic mass.