do now! have a look through your test!. moles! equal masses of different elements will contain...

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Page 1: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Do now!

Have a look through your test!

Page 2: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Moles!

Page 3: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Moles!

Equal masses of different elements will contain different numbers of atoms (as atoms of different elements have different masses)

Page 4: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Moles!

It is sometimes useful for physicists and chemists (but we don’t care about them) to compare the number of atoms or molecules in an amount of substance.

To do this we use the idea of moles.

A chemist

Page 5: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Moles!

• One mole of a substance contains the same number of molecules/atoms as in 12 grams of carbon-12.

• This number (of atoms or molecules) is known as the Avogadro constant (NA) which is equal to 6.02 x 1023

You need to learn this definition.

Page 6: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

How big is 6 x 1023?

Imagine the whole of the United states

You are here!

Page 7: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

How big is 6 x 1023?

Imagine the whole of the United states covered in unpopped popcorn

Page 8: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

How big is 6 x 1023?

Imagine the whole of the United states covered in unpopped popcorn to a depth of six miles!

Page 9: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

How big is 6 x 1023?

Imagine the whole of the United states covered in unpopped popcorn to a depth of six miles! Count the grains and that is 6 x 1023!

600000000000000000000000

Page 10: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Moles!

For example, Hydrogen (H2) has a relative molecular mass of 2, so 2 grams of hydrogen (one mole) contains the same number of molecules as atoms in 12g of carbon-12 (6.02 x 1023)

YouTube - Happy Mole Day to You Chemistry SongYouTube - Junior Chemistry: The Mole 1YouTube - The Mole - Amadeo Avogadro's Number

Page 11: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Moles!

It follows therefore that 7g of lithium (atomic mass 7), 20g neon (atomic mass 20) or 39 g potassium (atomic mass 39) all contain the same number of atoms (1 mole or 6.02 x 1023 atoms)

Page 12: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Moles!

• The number of moles of a substance can thus be found by dividing the mass of substance by its relative atomic or molecular mass

n = mass/RAM

Page 13: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Example

How many moles of sulphur atoms are there in 80g of sulphur? How many grams of carbon would have the same number of atoms?

Page 14: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Example

How many moles of sulphur atoms are there in 80g of sulphur? How many grams of carbon would have the same number of atoms?

N = mass/RAM = 80/32 = 2.5 moles

Page 15: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Example

How many moles of sulphur atoms are there in 80g of sulphur? How many grams of carbon would have the same number of atoms?

N = mass/RAM = 80/32 = 2.5 moles

Mass of carbon = RAM x n = 12 x 2.5 = 30 g

Page 16: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Relative formula mass

We can use the idea of moles and apply it to molecules using relative formula mass.

C2H5OH

RFM = (2 x 12) + (6 x 1) + (1 x 16) = 46

46g of ethanol = I mole of ethanol molecules

Page 17: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Let’s try some questions!

Page 81Questions 1 to 8

Page 18: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Can you read through the “Moles and

gases” section page 96 and 97?

Page 20: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Equal volumes

Luckily, equal volumes of gas contain the same number of particles (at the same temperature and pressure)

Page 21: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Equal volumes

For example, 1 litre of nitrogen contains the same number of molecules as there are atoms in one litre of Argon.

A litre is 1000 cm3 or 1 dm3

Page 22: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Mole of gas

One mole of any gas occupies 24 dm3 (24000 cm3) at room temperature and pressure (25°C and 1 atmosphere)

You will be given this in a

question

Page 23: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

At r.t.p. (25°C and 1 atmosphere)

Moles of gas = volume (cm3)/24000 = volume (dm3)/24

Learn this!

Page 24: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Standard temperature (0°C) and pressure (s.t.p.)

Page 25: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

More questions!

Page 26: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Moles in solution

Page 27: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Concentration/molarity

1M or 1 mol/dm3 means there is one mole of a substance dissolved in 1 dm3 (or 1000 cm3) of solution

Page 28: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

# of moles = concentration x volume (cm3)/1000

You need to know this too!

Page 29: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Let’s do some more reading and then try

some more questions! (pages 344 to 347)

Page 30: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Working out the formula

Page 31: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Working out the formula

• 1.4 g of Nitrogen reacts with 0.3 g of hydrogen to form a compound. What is the formula of the compound?

Page 32: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Working out the formula

• 1.4 g of Nitrogen reacts with 0.3 g of hydrogen to form a compound. What is the formula of the compound?

• First work out the number of moles

• 1.4g Nitrogen = mass/RAM = 1.4/14 = 0.1

• 0.3g hydrogen = mass/RAM = 0.3/1 = 0.3

Page 33: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Working out the formula

• 1.4 g of Nitrogen reacts with 0.3 g of hydrogen to form a compound. What is the formula of the compound?

• Work out the ratio of the number of moles of each element to the lowest whole numbers N : H

0.1 : 0.31 : 3

Page 34: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Working out the formula

• 1.4 g of Nitrogen reacts with 0.3 g of hydrogen to form a compound. What is the formula of the compound?

• Therefore there are 3 times as many hydrogen atoms as N atoms in the compound. The formula must be NH3 (ammonia)

Page 35: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Working out the formula

• A student adds 4.8 g of magnesium to excess dilute hydrochloric acid. What mass of magnesium chloride would be made?

Page 36: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Working out the formula

• A student adds 4.8 g of magnesium to excess dilute hydrochloric acid. What mass of magnesium chloride would be made?

• First write the balanced equation

Mg + 2HCl MgCl2 + H2

Page 37: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Working out the formula

• A student adds 4.8 g of magnesium to excess dilute hydrochloric acid. What mass of magnesium chloride would be made?

• Find out how many moles of magnesium are being used

# moles = mass/RAM = 4.8/24 = 0.2 moles

Page 38: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Working out the formula

• A student adds 4.8 g of magnesium to excess dilute hydrochloric acid. What mass of magnesium chloride would be made?

• From the equation we can see the number of magnesium atoms is the same as the number of magnesium chloride “molecules”. So if 0.2 moles of Mg are used we should produce 0.2 moles of MgCl2

Mg + 2HCl MgCl2 + H2

Page 39: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Working out the formula

• A student adds 4.8 g of magnesium to excess dilute hydrochloric acid. What mass of magnesium chloride would be made?

• Work out the mass of 0.2 moles of MgCl2

RFM (RMM) = 24 + (2 x 35.5) = 95

Mass of 0.2 moles of MgCl = 0.2 x 95 = 19g

Page 40: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

Let’s try some more questions!Pages 82 and 83

Read through the sheet first!

Norwegian just discovering the cost of a beer in Oslo

Page 41: Do now! Have a look through your test!. Moles! Equal masses of different elements will contain different numbers of atoms (as atoms of different elements

I feel a test coming on moles!

Thursday 19th June