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5s and 6s Clevedon Science > C5 > Flashcards

C5 Flashcards

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1
Q

What is the molar mass of a substance?

A

The molar mass is the relative formula mass of a substance in grams (measured in g/mol).

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2
Q

What is the relative formula mass of calcium hydroxide, Ca(OH)2?

A

(Ca = 40) (O = 16) (H = 1) Mr of Ca(OH)2 = 40 + 16 + 1 + 16 + 1 = 74

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3
Q

What is the formula triangle for calulating moles in solids?

A
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4
Q

Calcium carbonate decomposes to form calcium oxide and carbon dioxide when it is heated. What mass of carbon dioxide is made from 100 g of calcium carbonate?

A

44g

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5
Q

What is the molecular formula of a substance?

A

The molecular formula of a substance is the actual number of each type of atom in one unit of the substance.

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6
Q

What is the empirical formula of a substance?

A

An empirical formula is the simplest whole number ratio of each type of atom in a compound.

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7
Q

What is the empirical formula of C6H14?

A

C3H7

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8
Q

What is the percentage by mass of hydrogen in sodium hydroxide NaOH?

A

2.50%

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9
Q

What is concentration measured in?

A

Concentration is commonly measured in g/dm3 or in mol/dm3.

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10
Q

What is the solvent?

A

The solvent is the liquid that does the dissolving

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11
Q

What is the solute?

A

The solute is the substance that is dissolved

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12
Q

How do you convert cm3 to dm3 and vice versa?

A

Multiply by 1000/Divide by 1000

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13
Q

What does dilution mean?

A

When a solution is diluted, more solvent is added to it so that it becomes less concentrated.

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14
Q

What is the concentration formula triangle?

A
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15
Q

What does GDA stand for?

A

Guideline daily amounts. A GDA is the amount of nutrient regarded as suitable to maintain a healthy body

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16
Q

What does the PH scale show?

A

The pH scale gives a measure of how acidic or alkaline a solution is. It normally runs from 0 (most acidic) to 14 (most alkaline). A neutral substance is pH 7 at 25°C.

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17
Q

What does an indicator do?

A

An indicator changes colour depending on the properties of the substance it is added to

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18
Q

What are the three main indicators.

A

Litmus, phenolphthalein, universal indicator

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19
Q

What colour is red litmus paper in acid? In alkali?

A

Stays red in acids, turns blue in alkalis.

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20
Q

What colour is blue litmus paper in acid? In alkali?

A

Turns red in acids, stays blue in alkalis.

21
Q

What colour is phenolphthalein in acid? In alkali?

A

Colourless in acids, pink in alkalis

22
Q

Describe what the ph scale looks like using Universal Indicator

A
23
Q

Describe the shape of a pH curve when an acid is added to an alkali?

A
24
Q

Describe the shape of a pH curve when an alkali is added to an acid.

A
25
Q

Why do you need several titre readings?

A

It is important to repeat the titration several times to check that your titre value is consistent so that your calculations are reliable.

26
Q

Why are single colour change indicators used for titration?

A

If universal indicator is used, the colour changes gradually through a range of colours. On the other hand, a single indicator like litmus or phenolphthalein gives a sharp end-point where the colour changes suddenly

27
Q

Describe how to measure the volume of gas collected using the upwards displacement method.

A
28
Q

Why would you not measure the volume of carbon dioxide using the upwards displacement method?

A

Because carbon dioxide is partially soluble in water.

29
Q

What is the limiting reactant?

A

the limiting reactant is the one that is all used up at the end of the reaction

30
Q

What is the relationship between the limiting reactant and the amount of product formed?

A

The amount of product formed in a reaction is directly proportional to the amount of limiting reactant used

31
Q

What is the formula triangle for calulating moles in gases?

A
32
Q

What is a reversible reaction?

A

A reversible reaction can go in both directions - it can go forwards and backwards.

33
Q

At equilibrium, explain what is happening to the rate of formation of reactants and products.

A

When reversible reactions reach equilibrium, the forward and backward reactions are still happening, but at the same rate. This means that the concentrations of reactants and products do not change.

34
Q

What 3 factors can cchange the position of equilibrium?

A

Concentration, pressure and temperature

35
Q

Does a catalyst affect the position of equilibrium?

A

No, it just speeds up how quickly equilibrium is reached.

36
Q

Describe the conditions needed in the contact process.

A

A catalyst of vanadium(V) oxide, V2O5, a temperature of around 450 °C and atmospheric pressure

37
Q

What do strong acids ionise into in water?

A

Strong acids ionise fully into their constituent ions, e.g. HCL would ionise into H+ AND Cl-.

38
Q

Do weak acids fully ioinise?

A

No, they partially ionise and an equilibrium is set up

39
Q

Give an example of a weak acid

A

Ethanoic acid - vinegar

40
Q

Why do strong acids have a lower pH compared to weak acids of the same concentration?

A

Because they have more hydrohen ions in solution.

41
Q

Why does ethanoic acid react slower with magenisum than hydrochloric acid of the same concentration?

A

This is because the ethanoic acid will contain fewer hydrogen ions in a solution There will be fewer collisions between hydrogen ions and particles of the magnesium so the rate of reaction will be lower than for hydrochloric acid

42
Q

Explain why gas volume made depends on the concentration, not the acid strength

A

This is because both acids contain the same amount of acid reactant (same number of moles). The strength of the acid does not matter here.

43
Q

What happens to ions when they are in solution?

A

They break from theionic lattice and are free to move.

44
Q

What is a precipitation reaction?

A

In a precipitation reaction, ions collide with one another to form an insoluble product (one that does not dissolve in water). This is the precipitate.

45
Q

What is used to test for sulphate ions? What is a positive result?

A

Barium chholride -a whit eprecipitate o barium sulphate forms.

46
Q

What is used to test for halide ions?

A

Silver nitrate

agment–>

47
Q

List the colours of silver chloride, silver bromide and silver iodide precipitates.

A

White, cream, yellow

48
Q

What is a spectatotor ion?

A

An ion that does not take part in the reaction.

49
Q

What are the 3 main stages in preparing a dry sample of an insoluble salt?

A

Mixing, filtration and washing and drying.

5s and 6s Clevedon Science (6 decks)

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