The densities of gases a, b, and c at stp are 1.25 g/l, 2.86 g/l and 0.714 g/l, respectively. calculate the molar mass of each substance. identify each substance as ammonia (nh₃), sulfur dioxide (so₂), chlorine (cl₂), nitrogen (n₂) or methane (ch₄).

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Chemistry

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3 September, 16:04

The densities of gases a, b, and c at stp are 1.25 g/l, 2.86 g/l and 0.714 g/l, respectively. calculate the molar mass of each substance. identify each substance as ammonia (nh₃), sulfur dioxide (so₂), chlorine (cl₂), nitrogen (n₂) or methane (ch₄).

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Fatima Dawson · Answer 1

The molar mass of a, b and c at STP is calculated as below

At STP T is always = 273 Kelvin and, P = 1.0 atm

by use of ideal gas equation that is PV = nRT

n (number of moles) = mass/molar mass therefore replace n in the ideal gas equation

that is Pv = (mass/molar mass) RT

multiply both side by molar mass and then divide by Pv to make molar mass the subject of the formula

that is molar mass = (mass x RT) / PV

density is always = mass/volume

therefore by replacing mass/volume in the equation by density the equation

molar mass = (density xRT) / P where R = 0.082 L. atm/mol. K

the molar mass for a

= (1.25 g/l x0.082 L. atm/mol. k x273k) / 1.0atm = 28g/mol

the molar mass of b

= (2.86g/l x0.082L. atm/mol. k x273 k) / 1.0 atm = 64 g/mol

the molar mass of c

=0.714g/l x0.082 L. atm/mol. K x273 K) 1.0atm = 16 g/mol

therefore the

gas a is nitrogen N2 since 14 x2 = 28 g/mol

gas b = SO2 since 32 + (16x2) = 64g/mol

gas c = methaneCH4 since 12 + (1x4) = 16 g/mol