How do you find density of an unknown gas at STP?

hey

The mass of 1.12 liters of gas Y at STP is found to be 6.23 g. The density of gas y is...

10.6 g/L

15.6 g/L

0.200 g/L

5.56 g/L

Density is mass over volume so in this case

 

Density =  mass / volume =   6.23 g / 1/12 L   =   5.56 g / L