Question

1- A gas mixture is made by combining 6.9 g each of Ar, Ne, and an unknown diatomic gas. At STP, the mixture occupies a volume of 15.60 L.

2- 1.85 g of an unknown gas at 21 °C and 1.10 atm is stored in a 1.65-L flask.

-What is the density of the gas?​

-What is the molar mass of the gas?

3- An open flask sitting in a lab fridge looks empty, but we know that actually it is filled with a mixture of gases called air. If the flask volume is 5.00 L, and the air is at standard temperature and pressure, how many gaseous molecules does the flask contain?

Answer 1

1)

m = 6.9g of Ar

MW Ar = 39.9

mol = 6.9/39.9 = 0.1729 mol Ar

m = 6.9 g of Ne

MW ne = 20.1797

mol = masS/MW = 6.9/20.18 = 0.341 mol of Ne

mass of = 6.9

MW = ?

1 mol STP = 22.4 L

then

15.6/22.4 = 0.69642 mol present

NT = n1+N2*N3

N3 = NT-N1-N2 = 0.69642 -0.1729 -0.341 = 0.18252

MW = mass/mol = 6.9/(0.18252) = 37.804 g

nearest diatomic substance is F2

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