Question 1
A. Empirical formula is C8H8O3
B. Molecular formula is C8H8O3
Question 2.
A. Empirical formula is CH2
B. Molecular formula is C4H8
Explanation:
Question 1:
A. Determination of the empirical formula:
Carbon (C) = 63.2%
Hydrogen (H) = 5.26%
Oxygen (O) = 31.6%
Divide by their molar mass
C = 63.2/12 = 5.27
H = 5.26/1 = 5.26
O = 31.6/16 = 1.975
Divide by the smallest
C = 5.27/1.975 = 2.7
H = 5.26/1.975 = 2.7
O = 1.975/1.975 = 1
Multiply through by 3 to express in whole number
C = 2.7 x 3 = 8
H = 2.7 x 3 = 8
O = 1 x 3 = 3
Therefore, the empirical formula for the compound is C8H8O3
B. Determination of the molecular formula of the compound.
From Avogadro's hypothesis, 1 mole of any substance contains 6.02×10²³ molecules.
Now from the question given, we were told that 1 molecule of the compound has a mass of 2.53×10¯²² g.
Therefore, 6.02×10²³ molecules will have a mass of = 6.02×10²³ x 2.53×10¯²² = 152.306 g
Therefore, 1 mole of the compound = 152.306 g
The molecular formula of the compound can be obtained as follow:
[C8H8O3]n = 152.306
[(12x8) + (1x8) + (16x3)]n = 152.306
[(96 + 8 + 48 ]n = 152.306
152n = 152.306
Divide both side by 152
n = 152.306/152
n = 1
The molecular formula => [C8H8O3]n
=> [C8H8O3]1
=> C8H8O3
Question 2:
A. Determination of the empirical formula of the compound.
Mass sample of compound = 0.648 g
Carbon (C) = 0.556 g
Mass of Hydrogen (H) = mass sample of compound – mass of carbon
Mass of Hydrogen (H) = 0.648 – 0.556
Mass of Hydrogen (H) = 0.092 g
Thus, the empirical formula can be obtained as follow:
C = 0.556 g
H = 0.092 g
Divide by their molar mass
C = 0.556/12 = 0.046
H = 0.092/1 = 0.092
Divide by the smallest
C = 0.046/0.046 = 1
H = 0.092/0.046 = 2
Therefore, the empirical formula of the compound is CH2.
B. Determination of the molecular formula of the compound.
Mole of compound = 0.5 mole
Mass of compound = 28.5 g
Molar mass of compound =.?
Mole = mass /Molar mass
0.5 = 28.5/ Molar mass
Cross multiply
0.5 x molar mass = 28.5
Divide both side by 0.5
Molar mass = 28.5/0.5 = 57 g/mol
Thus, the molecular formula of compound can be obtained as follow:
[CH2]n = 57
[12 + (1x2)]n = 57
14n = 57
Divide both side by 14
n = 57/14
n = 4
Molecular formula => [CH2]n
=> [CH2]4
=> C4H8.
