Chemistry

5072Avogadro’s Constant

Mass of 1 atom• What is the mass of 1 proton?

1.67 X 10-24go What is the mass of 1 neutron?

1.67 X 10-24go What is the mass of one Hydrogen atom?

1.67 X 10-24gBecause hydrogen atom has only one proton

Mass of 1 atom ctd…

• What is the mass of 1 carbon atom?

12 X 1.67 X 10-24go What is the mass of 1 sodium atom?

23 X 1.67 X 10-24g

Molar mass

He S

Mg C

42

3216

2412

12 6

Let’s take the mass number as the mass in gram, how many atoms are there? (i.e. how many atoms are there in 4g of He?)

Avogadro’s constant

• Well, you know that given the mass number in grams, there are 6 X 1023 atoms/particles.

• 6 X 1023 is a constant number and this is termed as Avogadro’s constant.

• 4g of He, 32g of S, 24g of Mg and 12g of C contain 6 X 1023 particles. The mass which gives 6 X 1023 particles is termed as Molar mass!

Mole• One mole of any substance contains 6 X 1023 of particles.

• Therefore, molar mass of Na is 23g/mol.

• How about molar mass of:a)Znb)Sic)Ard)Ca

Analogy

Mass of 1 orange = mass of 1 apple = 10g

If the basket can contains 2 apples and 2 oranges, what is the mass of the basket now?

Mass of basket = 0g

40g

If one container can take in 10 baskets, what is the mass of the container? 400g

Analogy ctd…

Mass of 1 orange = mass of 1 apple = 10g

If the basket can contains 5 apples and 5 oranges, what is the mass of the basket now?

Mass of basket = 0g

100g

If one container can take in 10 baskets, what is the mass of the container?

1000g

Analogy

Mass of 1 orange = mass of 1 apple = 10g

If the basket can contains 2 apples and 2 oranges, what is the mass of the basket now?

Mass of basket = 0g

40g

If 1 container can take in 10 baskets, what is the mass of the container?

400g

proton neutron

nucleus

Mass number

Molarmass

Avogadro’s constantmole

Mole• 1 mole of any substance contains 6 X 1023 particles.

• How many particles are there in 2 moles of Na?1.2 X 1024 particles of Na

o How many particles are there in 3 moles of C?1.8 X 1024 particles of C

o How many particles are there in 0.25 of Ti?1.5 X 1023 particles of Ti

Mole ctd…• If there are 4 X 1023 particles of Mg, how many moles of Mg are there?4 X 1023 particles = 0.667 moles (3 sf)6 X 1023 particles

• If there are 1.5 X 1022 particles of He, how many moles of He are there?1.5 X 1022 particles = 0.0250 moles (3 sf) 6 X 1023 particles

Mole

Number of particles

X (6X1023) ÷ (6X1023)