Answer :
The number of moles of indicated substance in each sample is -
a) 6.14 x 10⁻⁴ mol
b) 3.1 x 10⁵ mol
c) 0.4 mol
d) 2.45 mol
e) 0.16 mol
To calculate number of moles of each substance in sample -
a) Sulfur trioxide
Given mass = 49.2 mg = 0.0492 g
Molar mass = 80.06 g/mol
Number of moles of sulfur trioxide = Given mass
Molar mass
= 0.0492g = 6.14 x 10⁻⁴mol
80.06 g/mol
b) Lead(iv) oxide
Given mass = 7.44 x 10⁴ kg = 7.44 x 10⁷ g
Molar mass = 239.2 g/mol
Number of moles of lead(iv)oxide = Given mass
Molar mass
= 7.44 x 10⁷g = 3.1 x 10⁵mol
239.2 g/mol
c) Chloroform (CHCl₃)
Given mass =59.1 g
Molar mass = 119.38 g/mol
Number of moles of chloroform = Given mass
Molar mass
= 59.1 g = 0.4 mol
119.38 g/mol
d) Trichloroethane (C₂H₃Cl₃)
Given mass = 3.27 mg = 0.00327 g
Molar mass = 133.4 g/mol
Number of moles of trichloroethane = Given mass
Molar mass
= 0.00327 g = 2.45 mol
133.4 g/mol
e) Lithium hydroxide
Given mass = 4.01 g
Molar mass = 23.95 g/mol
Number of moles of Lithium hydroxide = Given mass
Molar mass
= 4.01 g = 0.16 mol
23.95 g/mol
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Final answer:
Number of moles of the elements boron is 2, manganese is 1, mercury is 0.50, bariumis 0.36, and lead is 0.19.
Explanation:
To calculate the number of moles of a substance, you can use the formula:
Number of moles = [tex]\frac{Mass of the sample (g)}{Molar mass of the substance (g/mol)}[/tex]
For each substance, you would first need to know its molar mass:
- Boron (B) has a molar mass of about 10.81 g/mol.
- Manganese (Mn) has a molar mass of about 54.94 g/mol.
- Mercury (Hg) has a molar mass of about 200.59 g/mol.
- Barium (Ba) has a molar mass of about 137.33 g/mol.
- Lead (Pb) has a molar mass of about 207.2 g/mol.
Applying the formula:
- a. Number of moles of Boron = 21.6 g / 10.81 g/mol = 2.00 moles
- b. Number of moles of Manganese = 54.9 g / 54.94 g/mol ≈ 1.00 mole
- c. Number of moles of Mercury = 100.3 g / 200.59 g/mol ≈ 0.50 moles
- d. Number of moles of Barium = 50 g / 137.33 g/mol ≈ 0.36 moles
- e. Number of moles of Lead = 40 g / 207.2 g/mol ≈ 0.19 moles
