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OCR A LEVEL CHEMISTRY > ACID AND REDOX > Flashcards

ACID AND REDOX Flashcards

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1
Q

Which element do all acids contain?

A

Hydrogen

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2
Q

What happens when an acid is dissolved in water?

A

When an acid is dissolved in water, it releases hydrogen ions as protons, H+, into the solution

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3
Q

What is the equation that shows hydrogen chloride gas dissolving to form an aqueous solution?

A

HCl (g) + aq ———–> H+ (aq) + Cl- (aq)

+aq shows the excess of water present

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4
Q

What is an example of a strong acid?

A

Hydrochloric acid

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5
Q

What happens to a strong acid when placed in an aqueous solution?

A

The strong acid releases all its hydrogen atoms into solution as H+ ions

It completely dissociates in an aqueous solution

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6
Q

What happens to a weak acid when placed in an aqueous solution?

A

A weak acid only releases a small proportion of its available hydrogen atoms into solution as H+ ions.

It partially dissociates in aqueous solution.

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7
Q

What is an example of a weak acid?

A

Ethanoic acid - Ch3COOH

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8
Q

Why is ethanoic acid a weak acid?

A

A molecule of ethanoic acid contains 4 hydrogen atoms.

But only the hydrogen atom on the COOH group is released as H+

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9
Q

What is a base?

A

A base neutralises an acid to form a salt

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10
Q

What are example of bases?

A

Metal oxides
Metal hydroxides
Metal carbonates
Ammonia, NH3

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11
Q

What is an Alkali?

A

An alkali is a base that dissolves in water releasing hydroxide ions (OH-) into the solution.

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12
Q

What is the equation that shows alkali sodium hydroxide dissolving in water?

A

NaOH releases hydroxide ions as it dissolves in water

NaOH (s) + aq ——–> Na+ (aq) + OH- (aq)

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13
Q

What is the formula of hydrochloric acid?

A

HCl

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14
Q

What is the formula of sulfuric acid?

A

H2SO4

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15
Q

What is the formula of nitric acid?

A

HNO3

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16
Q

What is the formula of Ethanoic acid?

A

CH3COOH

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17
Q

Name 4 common acids

A

Hydrochloric acid
Sulfuric acid
Nitric acid
Ethanoic acid

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18
Q

Name 3 common metal oxide bases

A

MgO - Magnesium oxide
CaO - Calcium oxide
CuO - Copper oxide

19
Q

Name 3 common metal carbonate bases

A

Na2CO3 - Sodium carbonate
CaCO3 - Calcium carbonate
CuCO3 - Copper carbonate

20
Q

Name 3 common Alkali bases

A

NaOH - Sodium hydroxide
KOH - Potassium hydroxide
NH3 - Ammonia

21
Q

What are the products of a neutralisation of acid

A

Acid + metal oxide/hydroxide —-> Salt + water

22
Q

How do you form a salt from an acid?

A

The hydrogen in the acid is replaced by a metal or ammonium ion to form the salt

E.g. Hcl —–> NaCl

23
Q

What do you use to neutralise an acid?

A

A metal oxide or metal hydroxide

To form a salt and water only

24
Q

Acid + Alkali —->

A

Acid + Alkali —–> salt + water

25
Q

Carbonates neutralise acids to form…

A

salt + water + carbon dioxide gas

26
Q

Whats the differenc between a strong and a weak acid?

A

Strong acid fully dissociates in aqueous solution

Weak acid partially dissociates in aqueous solution

27
Q

Neutralisation of an acid

A

The H+ ions react with a base to form a salt + water.

H+ is replaced by metal or ammonium ions from base

28
Q

With alkalis, all reactants for neutralization are…

A

Aqueous

29
Q

What is a titration?

A

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

30
Q

Titrations can be used for:

A

Finding the concentration of a solution
Identification of unknown chemicals
Finding the purity of a substance

31
Q

Why is finding the purity of a substance important?

A

Important for pharmaceuticals

Just a tiny amount of impurity in a drug could cause a great deal of harm to a patient

32
Q

Volumetric flask typical tolerances

A

100cm^3 +/- 0.2cm^2

250cm^3 +/- 0.3cm^3

33
Q

Experimentally preparing standard solutions procedure:

A

Solid weighed + dissolved in beaker using less distilled water than needed to fill volumetric flask

Transfer to volumetric flask + last traces rinsed into flask with distilled water

Add distilled water dropwise until bottom of meniscus matches up with the mark

Flask inverted slowly several times to mix, if not titration results will be inconsistent

34
Q

Pipette Typical tolerances

A

10 cm^3 +/- 0.04cm^3

25cm^3 +/- 0.06 cm^3

Burette: 50cm^3 +/- 0.1

35
Q

How is a burette measured and recorded?

A

Burette is recorded to the nearest half division, to 2dp (last 5 or 0)

36
Q

Acid - base titration procedure

A

Add measured volume one solution to conical flask with pipette

Add other solutions to burette, recording initial reading

Add few drops of indicator to conical flask

Run solution from burette into conical flask, swirling it, until it reaches the end point

Record first reading

1st titre carried out quickly to get approx, then repeat accurately adding solution dropwise as end point approached. Carry out until two accurate titres are concordant (within 0.1cm^3)

37
Q

What is the oxidation number of oxygen?

A

-2

38
Q

What is the oxidation number of hydrogen?

A

+1

39
Q

What is the oxidation state of fluorine?

A

-1

40
Q

What is the oxidation state of ions

A

Charge on the ions

41
Q

What are the special cases in oxidation numbers

A

H in metal Hydrides: -1

O in peroxides: -1 (02 ^2-)

O boded to F: +2

42
Q

Reduction is

A

Gain of electrons

Decrease in oxidation numbers

43
Q

Oxidation is

A

Loss of electrons

Increase in oxidation numbers

OCR A LEVEL CHEMISTRY (48 decks)

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