Question #b7884

1 Answer
Stefan V.
Jan 28, 2015

The relative molecular mass of the gas is #"39.2 g/mol"#.

A very important thing happens at STP with ideal gases: 1 mole of any ideal gas occupies #"22.4 L"# - the molar volume of a gas. Since density is defined as mass per unit volume, you can automatically find the mass of 1 mole of gas (notice that I've converted #"1 L"# to 1 #"dm"^3#)

#rho = m/V => m = rho * V_("molar") = "1.750 g/dm"^3 * "22.4 dm"^3#

#m = "39.2 g"#

Therefore, the gas' molar mass is

#"molar mass" = ("39.2 g")/("1 mole") = "39.2 g/mol"#

This is pretty close to #"Ar"#'s molar mass, so that could be the identity of the gas.

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