Analysis of the Earth and Environment Lecture 3: Moles and Molar masses

Question 1

What is Avogadro’s number?

Answer 1

6.022 x 10^23

Question 2

Define a mole

Answer 2

A mole is a certain amount of things or particles.

Similiar to the word ‘Dozen’ meaning 12.
A ‘mole’ means 6.022 x 10^23.

Moles are usually associatied with very small particles, e.g. an atom or molecule

Question 3

What is the molar mass the same number as?

Answer 3

The atomic mass

Question 4

If the amount of moles is provided you can use this to calculate the amount of atoms present.

Answer 4

For example,

If there is 4 moles of carbon atoms, you times the amount of moles by avogadris number

4 x 6x10²³
(4x6=24)
24 x 10²³
(shift decimal place to the left)
2.4 x (10x10²³/10²⁴)
Conlcusion:
2.4 x 10²⁴
2.4 x 10²⁴ carbon atoms

Question 5

How would you convert the number of atoms to subatomic particles?

Answer 5

If you have the number of atoms, to calculate the number of electrons simply times the number of atoms by the number of electrons present in the atom of that element.

For example:
If we have 4 moles of carbon / 2.4 x 10²⁴ carbon atoms, and we wanted to calculate the amount electrons present in the 4 moles.

First find out how many electrons present in carbon atoms (6). And then multiply the amount of carbon atoms by that number.
6 x 2.4 x 10²⁴
(6x2.4=14.4)
14.4 x 10²⁴
1.44 x 10²⁵
Conlusion:
1.44 x 10²⁵ electrons present

Question 6

How would you convert the number of moles of a chemical compound into molecules?

Answer 6

The method of calculating the number of molecules through the amount of moles of a compound is the same as converting amount of moles to amount of atoms.

For example,
5 moles of methane (CH4)
5(moles) x 6.022x10²³
(5x6=30)
30x10²³
3.0x10²⁴

there is 3.0x10²⁴ molecules in 5 moles of methane.

Question 7

How would you find the specific number of atoms in a certain amount of moles of a chemical compound?

Answer 7

You would need to multiply the amount of moles by the amount of atoms in the molecule. For example, if you had 5 moles of methane (CH4), and you wanted to calculate the amount of hydrogen atoms present in the 5 moles.

First multiply the amount of moles by the amount of hydrogen in atoms in the molecule (4).
5 x 4 = 20
Then
20 x (6.22x10²³)
(20x6=120)
120 x 10²³
1.2 x 10²⁵

Conclusion: 1.2 x 10²⁵
atoms of hydrogen present.

Question 8

What is the formula for calculating molar concentration?

Answer 8

Molar concentration is the moles per litre of solution. Or mol/Litre.

           N M =    ----------
           V

M = Molar concentration
N = Moles of solute
V = Litres of solution