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GCSE Chemistry > C5 > Flashcards

C5 Flashcards

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1
Q

What does purity mean?

A

A substance that only contains one compound or element throughout (not mixed with anything)

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2
Q

How can you work out whether a mixture is pure or not?

A

A chemically pure substance, it will melt at a specific temperature- you can use this by melting the substance and comparing your melting point with the recorded melting point of the pure substance
Impurities will decrease the melting point and increase the melting range, so the lower the melting point is compared to the recorded one, and the greater the range is, the more impure it is

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3
Q

What’s the opposite of a pure substance?

A

A mixture

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4
Q

What are formulations?

A

Mixtures with precise quantities of specific substances in it

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5
Q

Give any 3 examples of formulations

A

Paints Alloys
Cleaning products Food
Fuels Drink
Hygiene products Fertilisers

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6
Q

What are the 2 phases of chromatography?

A

The mobile and stationary phase

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7
Q

What is the mobile phase?

A

Where the particles can move (liquid or gas)

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8
Q

What is the stationary phase?

A

Where the particles can’t move (solid or very thick liquid)

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9
Q

What is the formula for Rf value?

A

Rf = Distance travelled by solute / Distance travelled by solvent (should always be less than 1)

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10
Q

How can you reveal colourless spots on a chromatography?

A

Use a locating agent

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11
Q

How can you separate an insoluble solid from a solution?

A

Use filtration

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12
Q

How can you separate a soluble solid from a solution?

A

Use crystallisation- evaporate some of the solvent, then cool, then filter the crystals from the remaining solution

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13
Q

How can you separate mixtures of liquids or solutions?

A

Use simple distillation- evaporate then condense (liquids with very different boiling points will boil and condense at different points, so are separated)

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14
Q

What is quantitative chemical analysis?

A

How much is in it?

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15
Q

What is qualitive chemical analysis?

A

What’s in it?

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16
Q

What decides how far a substance travels on a chromatography?

A

Which phase their equilibrium favours (which they are more attracted to out of the mobile and stationary phase)

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17
Q

What colour is the precipitate when sodium hydroxide is mixed with Copper?

A

Cu(OH)2 is light blue and insoluble in excess NaOH

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18
Q

What colour is the precipitate when sodium hydroxide is mixed with Iron(II)?

A

Fe(OH)2 is green and insoluble in excess NaOH

19
Q

What colour is the precipitate when sodium hydroxide is mixed with Iron(III)?

A

Fe(OH)3 is red-brown and insoluble in excess NaOH

20
Q

What colour is the precipitate when sodium hydroxide is mixed with Calcium?

A

Ca(OH)2 is white and insoluble in excess NaOH

21
Q

What colour is the precipitate when sodium hydroxide is mixed with Zinc?

A

Zn(OH)2 is white but soluble in excess NaOH

22
Q

What colour precipitate is made when silver nitrate is mixed with Chloride?

A

White

23
Q

What colour precipitate is made when silver nitrate is mixed with Bromide?

A

Cream

24
Q

What colour precipitate is made when silver nitrate is mixed with Iodide?

A

Yellow

25
Q

How do you test for carbonates?

A

Add dilute acid, and if a carbonate is present, CO2 will be produced

26
Q

What colour do lithium ions cause the flame to turn?

A

Crimson (strong red)

27
Q

What colour do sodium ions cause the flame to turn?

A

Yellow

28
Q

What colour do potassium ions cause the flame to turn?

A

Lilac

29
Q

What colour do calcium ions cause the flame to turn?

A

Red

30
Q

What colour do copper ions cause the flame to turn?

A

Green

31
Q

What is flame emission spectroscopy used?

A

To analyse alloys

32
Q

What is the relative formula mass?

A

All the relative atomic masses of a compound added together

33
Q

What is the relative atomic mass?

A

The mass number (the number of protons + the number or neutrons)

34
Q

What are the 2 explanations for mass change during reactions?

A

1) If mass increases, it is likely that gas that was previously not in the reaction vessel has now entered
2) If mass decreases, it is likely that gas that was previously in the reaction vessel has now left

35
Q

What is a mole?

A

6x10^23

36
Q

Equation:

Moles, Mass, Atomic mass

A

Moles = Mass (g) / Atomic mass (g)

37
Q

Question:
How many moles are there in 66g of CO2?
C=12
O=16

A 
Answer:
1.5 moles
Working:
Moles = Mass / Atomic mass
Mass = 66g
Atomic mass = 12 + (16x2) = 44
66/44 = 1.5
38
Q

When do reactions stop?

A

When one of the reactants has run out

39
Q

How do you work out how much of a product you will make from given reactants? (theoretical yield)

A

1) Write a balanced equation
2) Find the atomic mass of the reactants and products you’re interested in
3) Find out how many moles there are in the substance you know the mass of, by using the equation moles = mass / atomic mass
4) Look at the ratio of moles between reactants and products in the balanced equation
5) Use the number of moles and the atomic mass to work out the mass in the equation mass = moles x atomic mass

40
Q

Question:
How much magnesium is need to make 100g of magnesium oxide in the reaction-
2Mg + O2 > 2MgO (already balanced)

A 
Answer:
60.3g
Working:
Relative atomic mass of Mg = 24.3
Relative atomic mass of MgO = 40.3
Moles = mass / atomic mass
Moles = 100 / 40.3
Moles = 2.48
Ratio of moles in Mg and MgO in balanced equation is 2:2 
Number of moles in Mg = 2.48
Mass = moles x atomic mass
Mass = 2.48 x 24.3
Mass = 60.3
41
Q

How can you use masses to get a balanced equation for a reaction?

A

1) Divide the mass by the atomic mass to work out moles
2) Divide the number of moles in each substance by the smallest amount of moles in the equation
3) Write the balanced equation putting those numbers in front of the correct reactants/products

42
Q

Question:
Noor burns a metal (X) in oxygen. There is a single product- X oxide. Given that 25.4g of X burns in 3.2g of oxygen, write a balanced equation for this reaction.
Atomic masses: X = 63.5, Oxygen = 16, X oxide = 143

A

Answer:
4X + O2 > 2X2O
Working:
CBA

43
Q

How can you work out the limiting reactants in a reaction?

A

1) Divide the mass of the reactant by the atomic mass to work out the moles
2) Divide the number of moles in each substance by the smallest amount of moles in the equation
3) Compare the ratio between the products in the balanced equation and the ratio between the moles

44
Q

What is the % yield?

A

(Mass of actual yield / Mass of theoretical yield) x 100

GCSE Chemistry (6 decks)

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