Determine the density of chlorine gas at 22.0°c and 1.00 atm.

Lets assume the gas is acting Ideally, then According to Ideal Gas Equation the density is given as,

                                            d  =  P M / R T           (1)
Where;
P  =  1 atm

M  =  70.90 g/mol

R  =  0.08206 atm.L.mol⁻¹.K⁻¹

T  = 22 °C + 273.15  =  295.15 K

Putting Values in eq. 1,

           d  =  (1 atm × 70.90 g/mol) ÷ (0.08206 atm.L.mol⁻¹.K⁻¹ × 295.15 K)

                                          density  =  2.92 g/L