10. Concepts in Chemistry: Moles

Question 1

What is the Mole?

Answer 1

Name given to a Certain Number of Particles (atoms, molecules or ions) equal to a number called Avogadro’s Constant

6.02 x 10 to power of 23

Question 2

Why is Avogadro’s Constant useful?

Answer 2

When you get that number of atoms or molecules of any element or compound then they WEIGH the same GRAMS and the Relative Atomic Mass (A) (or relative formula mass M) of the element or compound

Question 3

How do you use Avogadro’s Constant to calculate number of particles?

Answer 3

Number of Moles = Mass g (of element or compound / M (of compound) or A (of element)

I.e. Moles = Mass / M

Note: Use formula triangle to find the other variables

Question 4

How many magnesium atoms are there in 60g of magnesium? (A of Mg = 24)

Answer 4

ADD PICTURE

Question 5

What is Concentration?

Answer 5

• Measure of how crowded things are
• The more solute (solid you are dissolving) you dissolve in a given volume the more crowded / concentrated
• Concentration measured in grams per dm3 (g dm-3)
• 1 gram of stuff dissolved in 1 dm3 of solution has concentration of 1 g dm-3

Concentration (C) = Mass (m) of solute / Volume (V) of solute