Chemistry GCSE: C3 Quantitative Chemistry Flashcards Preview

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Flashcards in Chemistry GCSE: C3 Quantitative Chemistry Deck (36)
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1

What is the relative formula mass (Mr) of Li2O (lithium oxide)? Write down your workings.

 

Ar (relative atomic mass) of Li = 7

Ar (relative atomic mass) of O = 16

 

Li2 = 7 x 2 = 14

O = 16

Li2 + O = 14 + 16 = 30

2

What is the relative formula mass (Mr) of C3H8 (propane)? Write down your workings.

 

Ar (relative atomic mass) of C = 12

Ar (relative atomic mass) of H = 1

 

C3 = 12 x 3 = 36

H8 = 1 x 8 = 8

C3 + H8 = 36 + 8 = 44

3

What is the relative formula mass (Mr) of Ca(OH)2 (calcium hydroxide)? Write down your workings.

 

Ar of Ca = 40

Aof O = 16

Aof H = 1

 

Ca = 40

O + H = 16 + 1 = 17

(OH)2 = 17 x 2 = 34

Ca + (OH)2 = 40 + 34 = 74

4

What is the formula for calculating the percentage mass of an element in a compound?

 

Ar (relative atomic mass of element) x number of atoms x 100

               Mr (relative formula mass of compound)

5

What is the percentage mass of lithium in lithium oxide (Li2O)? Write down your workings.

 

Ar of Li  = 7 

Aof  O = 16

 

 

Mof Li2O

  • Li2 = 7 x 2 = 14
  • O = 16
  • Li2 + O = 14 + 16 = 30

Percentage mass of lithium in lithium oxide

  •  Li÷ Li2O  x 100 = 
  • (7x2) ÷ 30 x 100 =  
  • 14 ÷ 30 x 100 =  47%

                                

 

6

What is the percentage mass of hydrogen in propane (C3H8)? Write down your workings.

 

Ar of C = 12

Ar of H = 1

 

 

Mr of C3H8

  • C3 = 12 x 3 = 36
  • H8 = 1 x 8 = 8
  • C3 + H8 = 36 + 8 = 44

Percentage mass of hydrogen in propane

  • H÷ C3H8 x 100 =
  • (1x8) ÷ 44 x 100 =
  • 8 ÷ 44 x 100 = 18%

7

What is the percentage mass of oxygen in calcium hydroxide (Ca(OH)2)?Write down your workings.

 

Ar of Ca = 40

Ar of O = 16

Ar of H = 1

Mr of Ca(OH)2

  • Ca = 40
  • O + H = 16 + 1 = 17
  • (OH)2 = 17 x 2 = 34
  • Ca + (OH)2 = 40 + 34 = 74

Percentage mass of hydrogen in calcium hydroxide

  • O2 ÷ Ca(OH)x 100 =
  • (16x2) ÷ 74 x 100 = 
  • 32 ÷ 74 x 100 = 43%

 

8

If 6g of magnesium reacts completely with 4g of oxygen what mass of magnesium oxide is formed?

10g

9

When calcium carbonate is hated it breaks down to give calcium oxide and carbon dioxide.

calcium carbonate →calcium oxide + carbon dioxide

6.00g of calcium carbonate is heated, this gives 3.36g of calcium oxide. What mass of carbon dioxide was made?

 

Extension: Explain how you work this out.

 

6.00g - 3.36g = 2.64g

 

Extension: 

The total mass of products must equal the total mass of reactants. So to work out the mass of carbon dioxide yuo take away the mass of calcium oxide (product) from the mass of calcium carbonate (reactant).

10

Liam adds two reactants to an open conical flask on a mass balance. The starting mass is 10g. At the end of the reaction the mass is 8.95g. What might have caused the decrease in mass during the reaction?

 

  • One of the products was a gas
  • The gas will have left the conical flask decreasing the mass of the flask.

11

Sodium + Hydrochloric acid →Sodium chloride + Hydrogen

Jack reacts sodium with hydrochloric acid in an open (unsealed) conical flask. What will happen to the mass of the flask as the reaction takes place? Explain why this will happen.

 

  • The mass of the flask will decrease
  • Because, hydrogen is a gass and will be lost from the flask.

12

Jamie reacts 6g of magnesium with oxygen (from the air) by heating it. At the end of the reaction he finds he has 9.3g of magnesium oxide. 

 

How much oxygen was used in the reaction?

 

mass of magnesium oxide produced - mass of magnesium used = mass of oxygen used

9.3 - 6 = 3.3 g

13

HIGHER:

How many atoms are in 1 mole of lithium (Li)?

6.02 x 1023 (Avogadro's constant)

14

HIGHER:

How many molecules are in 1 mole of oxygen (O2)?

6.02 x 1023 (Avogadro's constant)

15

HIGHER:

How many atoms are in 1 mole of oxygen (O2)?

 2 x (6.02 x 1023): Each oxygen molecule has two oxygen atoms

1.204 x 1024

16

HIGHER:

How many molecules are in 1 mole of carbon dioxide (CO2)?

 6.02 x 1023

17

HIGHER:

How many atoms are there in 1 mole of carbon dioxide (CO2)?

 3 x (6.02 x 1023): Each carbon dioxide molecule is made from 3 atoms, 1 carbon atom and 2 oxygen atoms.

1.806 x 1024

18

HIGHER:

What is the mass of 5 moles of lithium oxide (Li2O)? Write down your workings.

Ar of Li = 7

Ar of O = 16

Mass of 1 mole of lithium oxide

  • Li2 = 7 x 2 = 14
  • O = 16
  • Li2 + O = 14 + 16 = 30g

Mass of 5 moles lithium oxide

  • 5 x 30g = 150g

19

HIGHER:​

What is the mass (in grams) of 3C3H8 (propane)? Write down your workings.

Ar (relative atomic mass) of C = 12

Ar (relative atomic mass) of H = 1

Mass of 1 mole of propane (C3H8)

  • C3 = 12 x 3 = 36
  • H8 = 1 x 8 = 8

  • C3 + H8 = 36 + 8 = 44g

Mass of 3 moles propane

  • 3 x 44g = 132g

20

HIGHER:

How many moles of water (H2O) are there in 36g?

Ar (relative atomic mass) of H = 1

Ar (relative atomic mass) of O = 16

Mass of 1 mole of water (H2O)

  • H2 = 1 x 2 = 2
  • O = 16
  • H2 + O = 2 + 16 = 18g

Moles of water in 36g

  • number of moles = total mass ÷ mass of 1 mole
  • 36 ÷ 18 = 2 moles

21

 HIGHER:

How many moles of ammonia (NH3) are there is 8.5g.

Ar (relative atomic mass) of N = 14

Ar (relative atomic mass) of H = 1

 

 

Mass of 1 mole of water (NH3)

  • N = 14
  • H3 = 1 x 3 = 3
  • N + H3 = 14 + 3 = 17

Moles of ammonia in 8.5g

  • number of moles = total mass ÷ mass of 1 mole
  • 8.5 ÷ 17 = 0.5 moles

22

HIGHER: 

3.5 g of Li reacts completely with 4g of O2 to produce 7.5 g of Li2O. Use this to work out a balanced equation for the reaction.

Ar (relative atomic mass) of Li = 7

Mr (relative formula mass) of O2 = 32 (16 x2)

Mr (relative formula mass of Li2O = 30 ( 14 x 2 + 16)

Write you answer out.

  • Li + O2 → Li2O
  • Moles of Li in 3.5 g = 3.5 ÷ 7 = 0.5
  • Moles of O2 in 4g = 4 ÷ 32 = 0.125
  • Moles of Li2O in 7.5 g = 7.5 ÷ 30 = 0.25
  • ratio of atoms/molecules = 0.5: 0.125: 0.25
  • To get whole number divide each by the smallest (0.125)
  • ratio of atoms/molecules = 4:1:2
  • Balanced equation = 4Li + 1O2 → 2Li2O

23

4Al + 3O2 → 2Al2O3

Calculate the number of moles of aluminium oxide formed when 135g of aluminum is burned in air.

 

 

  • 4Al + 3O2 → 2Al2O3
  • Number of moles of aluminium = mass of aluminium ÷ relative formula mass
  • 135 ÷ 27 = 5
  • Ratio of aluminium to aluminium oxide 4:2
  • There are half the number of moles of aluminium oxide as there are of aluminium
  • There will therefore be 5 x 0.5 = 2.5 moles of aluminium oxide

24

  • What volume does a mole of gas occupy at toom temperature (20oC) and pressure (1 atm)

  • 24 dm3

25

If you were given the mass of a gas, how would you calculate the volume it takes up?

Volume of gas (in dm3) = number of moles x 24, therefore..

Volume of gas (in dm3) = (mass ÷ relative formula mass) x 24

26

What is the volume of 80 g of oxygen at room temp and pressure?

Volume of gas (in dm3) = number of moles x 24

Volume of gas (in dm3) = (mass ÷ relative formula mass) x 24

= (80 ÷ 16) x 24 = 5 x 24 

= 120 dm3

27

What volume of ammonia is formed when 100 dm3 of nitrogen reacts with hydrogen.

N2 + 3H2 → 2NH3

N2 + 3H2 → 2NH3

The ratio of nitrogen to ammonia is 1:2

Therefore if you use 100 dm3 of nitrogen you will get 200 dmof ammonia.

 

28

What is the formula for working out the concentration of a solution in g/dm3?

Concentration (g/dm3) = mass of solute (g) ÷ volume of solvent (dm3)

29

What is the formula for working out the concentration of a solution in mol/dm3?

Concentration (mol/dm3) =  moles of solute ÷ volume of solvent (dm3)

30

If you were given the concentration of a solution (mol/dm3) and the volume (dm3), how would you calculate the number of moles of solute present?

moles of solute = Concentration (mol/dm3) x volume of solvent (dm3)