3.3 (b) relative atomic mass

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RELATIONSHIP BETWEEN “MOLE” AND “MASS”

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a) 1 mole atom of element / molecule have 6.02 x 1023

particles.

b) Scientist found that:i) mass of 1 mole atom of any element is Relative Atomic Mass in gram.

Mole of element / molecule

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ii) mass of 1 mole atom of any molecule is Relative

Molecular Mass or Relative Formula Mass in gram.

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Mass of 1 mole atom of:

i) element = Relative Atomic Mass in gram.

ii) molecule = Relative Molecular

Mass / Relative

Formula Mass in

gram.

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For example (element):

Relative Atomic Mass of sodium (Na)

= 23 g/mol

So, the mass of 1 mole atom of sodium (Na)

= 23 g

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Try it yourself!!

Relative Atomic Mass of magnesium (Mg) = 12 g/mol

So, the mass of 1 mole atom of magnesium (Mg)

= 12 g

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How about this?

The mass of 1 mole atom of argentum (Ag)

= 47 gSo, the Relative Atomic Mass of argentum (Ag)

= 47 g/mol

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For example (molecule):

Molecular formula of carbon dioxide = CO2

Relative Molecular Mass of CO2

= (12 X 1) + (16 X 2) = 44 g/mol

So, the mass of 1 mole CO2

= 44 g

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Try it yourself!!

Relative Molecular Mass of NaCl = 23 + 35.5

= 58.5 g/mol

So, the mass of 1 mole of NaCl

= 58.5 g

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How about this?

Relative Molecular Mass of KCl = 19 + 35.5 = 54.5 g/mol

So, the mass of 1 mole of KCl = 54.5 g

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Mass of

element

in gram

Number

of mole

of element

X=Relative

Atomic

Mass of

the element

MASS:

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Number of = mass of element in gram moles of Relative Atomic Mass element

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Mole of element Mass of element

X Relative Atomic Mass

/ Relative Atomic Mass

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Number

of mole

of molecule

=Mass of

molecule

in gram

Relative

Molecular

Mass@Relative

Formula

Mass of

the molecule

MOLE:

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Mole of molecule

X Relative Molecular Mass

Mass of molecule

Relative Molecular

Mass or Relative

Formula Mass

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Example 1:

What is the mole of 18 g of water? Calculate the molar mass of the water.

[Relative Atomic Mass: H=1; O=16]

Example 1:

What is the mole of 18 g of water? Calculate the molar mass of the water.

[Relative Atomic Mass: H=1; O=16]

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Answer:

Number of mole of water

= mass of H2O in gram

relative molecular mass

= 18 g

18 g/mol

= 1 mole

Answer:

Number of mole of water

= mass of H2O in gram

relative molecular mass

= 18 g

18 g/mol

= 1 mole

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Molar mass of water = mass of 1 mole of

molecule = 18 g

Molar mass of water = mass of 1 mole of

molecule = 18 g

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ACTIVITIES

TIME!!

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That’s all for today!

Thank you!