Question

a 707 mg sample of gas containing only carbon and oxygen occupies a volume of 452 ml at 63 C and 745 mmHg. identify the gas in the sample (R= 0.0821 L*atm/K*mol)

Answer 1

PV = nRT

where P = pressure, V = volume, n = moles, R = ideal gas constant, and T = temperature

since the units of R are L*atm/K*mol, the other constants should be changed accordingly.

pressure is given in mm Hg ----> to go from mmHg to atm, divide by 760 mmHg/1 atm

volume is given in mL ---> to convert mL to L, divide by 1000 mL/L

temperature is given in celcius ---> to convert to K, add 273.15

once you have your P, V, T values, plug everything into the equation and solve for n (moles)

Answer 2

now, once you have moles, you can solve for the molar mass, and thus, the identity of the gas

molar mass = (mass in grams) / (moles)

they give you mass in mg, so divide mg/1000 to convert to grams
you already have moles from the previous step

so from there, calculate molar mass.

now, since the compound is only made from carbon and oxygen, try to see what carbon-oxygen only gas would have your molar mass