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2 years ago

How to do this Q1 and Q2 Only want to know how to find molecular formula

Chemistry

1 answer:

Anestetic [448]2 years ago

5 0

Answer:

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.

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