Answer to Question #182856 in Chemistry for Kristagay Tulloch

Question

1. You have 42.04g of a sample of carbon. Calculate the number of moles in the carbon sample
2. 2.If you have 4.257 mol of Al(OH)3, the number of molecules you have is

3. A Canadian penny contains 0.106 mol of copper. How many atoms of copper are in a Canadian penny?

4.Iron (II) oxide is used in mascara and eye shadow because it provides a brown colour to the product.  “Pretty Eyes” mascara uses 0.15g of the Iron (II) oxide. Determine the number of “particles” (aka molecules) that would be present in the product.

5. Analysis of an ore of calcium shows that it contains 13.61g of calcium and 21.77g oxygen in a sample with a total mass of 46.28g. Calculate the mass percent of this compound.

6. Determine the % composition of Sodium Nitrate ?

Answer 1

Solution:

(1):

Molar mass of carbon (C) is 12.011 g/mol.

Hence,

(42.04 g C) × (1 mol C / 12.011 g C) = 3.50 mol C

Moles of carbon = 3.50 mol

(2):

One mole of any substance contains 6.022×10²³ atoms/molecules.

Hence,

Number of Al(OH)₃ molecules = (4.257 mol) × (6.022×10²³ molecules / 1 mol) = 2.56×10²⁴ molecules

Number of Al(OH)₃ molecules = 2.56×10²⁴ molecules

(3):

One mole of any substance contains 6.022×10²³ atoms/molecules.

Hence,

Number of copper atoms = (0.106 mol) × (6.022×10²³ atoms / 1 mol) = 6.38×10²² atoms

Number of copper atoms = 6.38×10²² atoms

(4):

Iron (II) oxide - FeO

The molar mass of FeO is 71.844 g/mol.

Hence,

(0.15 g FeO) × (1 mol FeO / 71.844 g FeO) = 0.002088 mol

One mole of any substance contains 6.022×10²³ atoms/molecules.

Hence,

Number of FeO molecues = (0.002088 mol) × (6.022×10²³ molecules / 1 mol) = 1.257×10²¹ molecules

Number of FeO molecues = 1.257×10²¹ molecules

(5):

%Ca = (Mass of Ca / Total mass of sample) × 100%

%Ca = (13.61 g / 46.28 g) × 100% = 29.41%

%Ca = 29.41%

%O = (Mass of O / Total mass of sample) × 100%

%O = (21.77 g / 46.28 g) × 100% = 47.04%

%O = 47.04%

(6):

Sodium nitrate - NaNO₃

The molar mass of NaNO₃ is 84.995 g/mol.

The molar mass of Na is 22.9898 g/mol.

The molar mass of N is 14.0067 g/mol.

The molar mass of O is 15.999 g/mol.

Hence,

%Na = (22.9898 / 84.995) × 100% = 27.05%

%N = (14.0067 / 84.995) × 100% = 16.48%

%O = (3×15.999 / 84.995) × 100% = 56.47%

%Na = 27.05%

%N = 16.48%

%O = 56.47%

Answers:

1) Moles of carbon = 3.50 mol;

2) Number of Al(OH)₃ molecules = 2.56×10²⁴ molecules;

3) Number of copper atoms = 6.38×10²² atoms;

4) Number of FeO molecues = 1.257×10²¹ molecules;

5) %Ca = 29.41%; %O = 47.04%;

6) %Na = 27.05%; %N = 16.48%; %O = 56.47%.