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Chemistry OCR A-Level > Chapter 4 > Flashcards

Chapter 4 Flashcards

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1
Q

What is the formula of hydrochloric acid?

A

HCl

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2
Q

What is the formula of sulfuric acid?

A

H₂SO₄

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3
Q

What is the formula of nitric acid?

A

HNO₃

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4
Q

What is the formula of ethanoic acid?

A

CH₃COOH

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5
Q

What is ethanoic acid also known as?

A

vinegar

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6
Q

What do all acids contain in their formulae?

A

hydrogen

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7
Q

When dissolved in water, what do acids release into the solution?

A

hydrogen ions as protons, H⁺

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8
Q

Why has + aq been included in this equation:

HCl(g) + aq –> H⁺(aq) + Cl⁻(aq)

A

To show that an excess of water is present

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9
Q

What is a strong acid?

A

1) releases all its hydrogen atoms into solution as H⁺ ions

2) completely dissociates in aqueous solution

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10
Q

What is a weak acid?

A

1) only releases a small proportion of its available hydrogen atoms into solution as H⁺ ions
2 )partially dissociates in aqueous solution

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11
Q

Are all compounds that contain hydrogen atoms acids?

A

no

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12
Q

Are most organic acids strong or weak?

A

weak

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13
Q

What is a base?

A

neutralises an acid to form a salt

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14
Q

What are some common types of bases?

A

1) metal oxides
2) metal hydroxides
3) metal carbonates

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15
Q

What is an alkali?

A

A base that dissolves in water releasing hydroxide ions, OH⁻ into the solution

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16
Q

acid + metal oxide/hydroxide –>

A

salt + water

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17
Q

CuO(s) + H₂SO₄(aq) –>

A

CuSO₄(aq) + H₂O(l)

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18
Q

CuO(s) + 2HCl(aq) –>

A

CuCl₂(aq) + H₂O(l)

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19
Q

acid + alkali –>

A

salt + water

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20
Q

What is the ionic equation of neutralisation to form water, H₂O(l)?

A

H⁺(aq) + OH⁻(aq) –> H₂O(l)

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21
Q

acid + metal carbonate –>

A

salt + water + carbon dioxide

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22
Q

ZnCO₃(s) + H₂SO₄(aq) –>

A

ZnSO₄(aq) + H₂O(l) + CO₂(g)

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23
Q

MgCO₃(s) + 2HCl(aq) –>

A

MgCl₂(aq) + H₂O(l) + CO₂(g)

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24
Q

Is H₂SO₄(aq) a strong or weak acid?

A

strong

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25
Q

Are HSO₄⁻(aq) ions trong or weak?

A

weak

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26
Q

Write an equation for the partial neutralisation of carbonic acid, H₂CO₃ with sodium hydroxide.

A

H₂CO₃(aq) + NaOH(aq) –> NaHCO₃(aq) + H₂O(l)

27
Q

Write an equation for the complete neutralisation of carbonic acid, H₂CO₃ with sodium hydroxide.

A

H₂CO₃(aq) + 2NaOH(aq) –> Na₂CO₃(aq) + 2H₂O(l)

28
Q

What is a titration?

A

A technique used to accurately measure the volume of one solution that reacts exactly with another solution

29
Q

What can titrations be used for?

A

1) finding the concentration of a solution
2) identification of unknown chemicals
3) finding the purity of a substance

30
Q

Why is checking purity an important aspect of quality control?

A

In pharmaceuticals, a tiny amount of an impurity in a drug could cause a great deal of harm to a patient

31
Q

What is a standard solution?

A

A solution of known concentration

32
Q

What is used to make up a standard solution very accurately?

A

volumetric flask

33
Q

What is the tolerance of a 100cm³ volumetric flask?

A

±0.20cm³

34
Q

What is the tolerance of a 250cm³ volumetric flask?

A

±0.30cm³

35
Q

How do you prepare a standard solution?

A

1) weigh solid accurately
2) dissolve solid in a beaker using less distilled water than will be needed to fill volumetric flask to mark
3) transfer solution to volumetric flask, last traces of solution are rinsed into the flask with distilled water
4) carefully fill flask to graduation line by adding distilled water a drop at a time until the bottom of the meniscus lines up exactly with the mark
5) invert volumetric flask several times to mix solution thoroughly

36
Q

When preparing a standard solution, what is the effect of filling the flask with water above the graduation line?

A

The solution will be too dilure and must be prepared again

37
Q

When preparing a standard solution, what is the effect of not inverting the flask?

A

Titration results are unlikely to be consistent

38
Q

What is the tolerance of a 10cm³ pipette?

A

±0.04cm³

39
Q

What is the tolerance of a 25cm³ pipette?

A

±0.06cm³

40
Q

What is the tolerance of a 50cm³ burette?

A

±0.10cm³

41
Q

When working out the mean titre, which values do you use?

A

The closest accurate titres

42
Q

How do you reject inaccurate titres?

A

By repeating titres until two agree with 0.10cm³

43
Q

What is oxidation number?

A

The number of electrons involved in bonding to a different element

44
Q

What is the oxidation number for elements?

A

0

45
Q

In oxidation numbers, is the sign placed before or after the number?

A

before

46
Q

What is the oxidation number of O?

A

-2

47
Q

What is the oxidation number of H?

A

+1

48
Q

What is the oxidation number of F?

A

-1

49
Q

What is the oxidation number of Na⁺, K⁺?

A

+1

50
Q

What is the oxidation number of Mg²⁺, Ca²⁺?

A

+2

51
Q

What is the oxidation number of Cl⁻, Br⁻, I⁻?

A

-1

52
Q

What are the exceptions of oxidation number rules?

A

1) H in metal hydrides
2) O in peroxides
3) O bonded to F

53
Q

What is the oxidation number of H in NaH/CaH₂?

A

-1

54
Q

What is the oxidation number of O in H₂O₂?

A

-1

55
Q

What is the oxidation number of O in F₂O?

A

+2

56
Q

sum of oxidation numbers =

A

total charge

57
Q

What is oxidation?

A

addition of oxygen

58
Q

What is reduction?

A

removal of oxygen

59
Q

What are redox reactions?

A

When reduction and oxidation happen at the same time

60
Q

What is reduction in terms of electrons?

A

gain of electrons

61
Q

What is oxidation in terms of electrons?

A

loss of electrons

62
Q

What is reduction in terms of oxidation number?

A

decrease in oxidation number

63
Q

What is oxidation in terms of oxidation number?

A

increase in oxidation number

64
Q

metal + acid –>

A

salt + hydrogen

Chemistry OCR A-Level (28 decks)

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