moles and Avogadros constant.

Question 1

What is the mole?

Answer 1

The amount of a substance that contains the same number of atoms or particles as 12g of carbon 12

Question 2

What is the value of the mole?

Answer 2

6.02x10^23 (avogadro’s constant)

Question 3

What is molar mass?

Answer 3

The mass of one mole of a substance

Question 4

What is an example of Mr?

Answer 4

Carbon = 12
Oxygen = 16
Nitrogen = 14

Question 5

What does the molar mass do?

Answer 5

It takes the same value as the atomic mass and helps calculate for
Moles = mass/ molar mass

Question 6

What is the units of molar mass?

Answer 6

G/mol

Question 7

When 0.22g of pure barium is added to water, how many moles of Barium have been added?

Answer 7

Moles = mass/mr
= 0.22/137.33
=16 x10^-4

Question 8

Modern pencils contain graphite rather than lead. In a pencil containing 0.642g of pure graphite, a form of carbon, calculate the amount in mol of graphite.

Using Avogadro’s constant, calculate how many carbon atoms are present in this sample of graphite.

Answer 8

Moles=mass/mr
=0.642/12
=0.0535

0.0535 x (6.02x10^23)
=3.22x10^22