A compound used in the manufacture of Saran is 24.7 % H, and 73.2 % Cl by mass.

Question

A compound used in the manufacture of Saran is 24.7 % H, and 73.2 % Cl by mass. The storage of 3.557 g of the compound in a 755-mL vessel at 0 degree C results in a pressure of 1.1 atm. What is the molecular formula of the compound: It takes 30 mL- of argon 40 s to effuse through a porous barrier. The same volume of a vapor of a volatile compound extracted from a Caribbean sponge takes 120 s to effuse through the same barrier under the same conditions. What is the molar mass of the compound Consider the reaction: 2NO(g) + O_2(g) right arrow 2NO_2(g) delta H = 113.1kJ. If delta H degree for N0_2 is 33.8 kJ/mole, Calculate delta H_r degree for NO(g).

Explanation / Answer

4.

24.7 g/1gH/molH = 24.7

73.2g/35.5gCl/molCl= 2.06

100-24.7-73.2 = 2.1% for an other element.

Something is wrong here and I suppose thet 24.7 is for C. Thus

24.7 g/12gC/molC = 2.05

73.2g/35.5gCl/molCl= 2.06

100-24.7-73.2 = 2.1% for an other element (identified as H

2.1 g/1gH/molH= 2.1

The ratio C:H:Cl is 1:1:1. The compound is (CHCl)x with a molar mass 48.5x g/mol.

Use the gas law pV=nRT = (m/M)RT

1.1atm x 0.775 L = (3.557g/48.5x) ·0.0821 L.atm/mol.K x 273K

x= 1.93 = 2

5.

Use Graham’s law for gas effusion

The rate of efusion r (mol/s but also mL/s), molar mass M for 2 gases 1 and.

r1/r2 = (M2/M1)1/2

molar mass of Ar = 40 g/mol

120s/40s = (Mx/40)1/2

Mx/40 = 9

Mx = 360 g/mol

6.

dH = 2xdHof,NO2 - 2xdHof,NO

113.1 = 2x33.8 – 2xdHof,NO

dHof,NO = … kJ

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