RT Replacing the n in the above molar mass equation, the molar mass can be expre

Question

RT Replacing the n in the above molar mass equation, the molar mass can be expressed as, mRT My gas PV Thus, the molar mass of a gas can be determined by measuring the temperature, pressure, volume and mass of a sample gas. 1. A compound has the empirical formula, CHCl. A 256-mLflask, at 100oCand 0.967atm, contains 0.800 g of the gaseous compound. Calculate the molar mass of this compound, and determine its molecular formula. Show your work. I00 °C. a. Complete the table below Volume of the gas in Liter (this 0.250 L is the volume of the flask) Temperature of the gas in 873.15 Kelvin Pressure of the gas in atm O, a Mass of the gas in gram 0.000 Gas constant, R, in the unit of 0.08 L atm. K mole i

Explanation / Answer

(1) a and b what did is correct.

in (b) molar mass = 0.800 * 0.0821 * 373.15 / (0.967 * 0.256) = 99.0 g/mol

(c) emperical formula mass = 1 (C) + 1 (H) + 1 (Cl) = 1 (12) + 1(1) + 1 (35.5) = 48.5

Molar mass = 99.0

n = molar mass / emperical formula mass

n = 99.0 / 48.5

n =

SO,

Molaecular formula = (emperical formula)n = (CHCl)2 = C2H2Cl2

(2)

Ideal gas equation,

P V = n R T

P V = (m/M) R T
M = (m / V) R T / P

M = d R T / P

M = 3.164 * 0.0821 * 273 / 1.00

M = 70.9 g/mol

Now,

3.164 g. of gas occupies 1 L volume,

then, 70.9 g. of gas occupies 70.9 / 3.164 = 22.4 L

SO, the gas with molar mass 71 is chlorine. Cl2

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