Answer all of the question in your lab notebook. You do not need to rewrite the

Question

Answer all of the question in your lab notebook. You do not need to rewrite the questions. Just provide the answers. Determine the empirical formula for these compounds: a. Cr 47.7% F 52.3% b. Na 42.1% P 18.9% O 39.0% c. K 60.0% C 18.S% N 21.5% d. P 7.5% 192 5% If the volume of a flask is 175 ml and the mass of the vapor of the flask is 0.2436 grams at 1.05 atm and 25 degree C, what is the molar mass of the gas? What is the formula and molar mass of the following compounds? a. Hexane b. Methanol c. Ethanol d. Dichloromethane e. Acetonitrile

Explanation / Answer

Q1.

empirical formula:

a)

assume this is by mass so

47.7 g of Cr, mol = mass/MW = 47.7/51.99610 = 0.917

52.3 g of F, mol = mass/MW = 52.3/18.998 = 2.752

ratio

2.752/0.917 = 3

so

CrF3

b)

mol of Na = mass/MW = 42.1/23 = 1.83

mol of P = mass/MW = 18.9/30.973762 =0.61

mol of O = mass/W = 39/16 = 2.44

ratio

Na/¨P = 1.83/0.61 = 3

O/P = 2.44/0.61 = 4

so

Na3PO4

c)

mol of K = mass/MW = 60/39.9 = 1.51

mol fo C =mass/MW = 18.5/12 = 1.54

mol fo N = mass/MW = 21.5/14 = 1.54

empricial KCN

d)

mol of P = mass/MW = 7.5/31 = 0.24

mol of I = mass/MW = 92.5/126.90447 = 0.73

ratio

0.73/0.24 = 3

PI3

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