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Chemistry > P1-Topic 4- Chemical Changes 2022 > Flashcards

P1-Topic 4- Chemical Changes 2022 Flashcards

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1
Q

What is oxidation?

A

Oxidation - When a substance gains oxygen

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2
Q

What is reduction?

A

Reduction - When a substance loses oxygen

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3
Q

what is a metal and oxygen reaction? 2

A

Metals + oxygen -> metal oxides

Known as oxidation reactions because the metals gain oxygen

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4
Q

What is the reactivity series of metals?

A

The series shows the metals in order of their reactivity

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5
Q

What are the trends in

reactivities of metals in reactions with acids/water? 4

A

Metals above H₂ in reactivity series react with acid to produce H₂

The more reactive the metal is, the quicker and more violent reaction with acid occurs

Metals below H₂ don’t react with acids.

Not all metals above H₂
react with water - mostly Group I and II metals.

Aluminium
is the borderline case

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6
Q

What is a displacement reaction?

A

A reaction where a more reactive metal displaces a less reactive metal from a
compound

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7
Q

what is the reactiviy of a metal related to.

A

The reactivity of a metal is related to its tendency to

form positive ions

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8
Q

how does a metal (K,Na,Li,Ca) react with water 2

A

higher the reactivity K,Na the react violently, very quik

Ca is more slow

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9
Q

how does a metal (Ca,Mg,Zn,Fe,Cu) react with an acid

A

the higher the reactivity the more quick the reaction is

Ca-very quick
Mg quick

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10
Q

How are unreactive metals found in Earth?

A

In their natural state (well, they are unreactive…)

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11
Q

How can metals less
reactive than carbon be
extracted? 4

A

by reduction with carbon

Carbon displaces the metal in a metal oxide

gets oxidised to form carbon oxides

Metal from the metal oxide gets reduced to the pure metal

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12
Q

How are metals more reactive than carbon extracted?

A

By electrolysis

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13
Q

what has been oxidised and reduced in 2Na + 2HCl -> 2NaCl + H₂?

A

sodium = 2Na -> 2Na(+) +2e-
Na has lost electrons & has been oxidised

2Cl- > 2Cl- has not been
oxidised or reduced

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14
Q

What is the general equation for a reaction between metals+ acids?

What type of reaction is this 2

A

Metal + acid → salt + hydrogen

Redox reaction, also a displacement reaction

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15
Q

Which metals in the reactivity series will react with acid?

A

Those above hydrogen

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16
Q

what are bases 2

A

chemical that can neutralise acids producing a salt + water

those soluble in water are called alkali’s

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17
Q

What is the general equation for the reaction between metal carbonate and acid?

A

Metal carbonate + acid → salt + water + carbon dioxide

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18
Q

What is the general equation for
the reaction between metal oxides
and acids?

A

Metal oxide + acid → a salt + water

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19
Q

What is a redox reaction?

A

A reaction where both oxidation and reduction occurs

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20
Q

How is a soluble salt formed?

A

a) React the excess acid with some insoluble chemical (e.g. metal oxide)
b) Filter off the leftovers
c) Crystallise the product

21
Q

What do acids and alkalis produce in aqueous solutions?

A

Acids produce hydrogen ions, alkalis produce hydroxide ions

22
Q

State the general equation for a neutralisation reaction in a short, ionic form. water

A

H(+) + OH(−) → H₂O

23
Q

What is the pH scale and what does a pH of 7 show?

A

The measure of acidity/alkalinity of a solution

neutral solution
7+ alkaline =purple
7- acidic= red

24
Q

What is a strong acid? 2

A

completely ionised in aqueous solution.

HCl→H+ +Cl-
hydrochloric, nitric and sulfuric acids.

25
Q

What is a weak acid?

A

partially ionised in aqueous solution

H₂CO₃ ⇌ H+ + HCO₃-
ethanoic, citric and carbonic acids

26
Q

What happens to pH scale as it decreases by 1 unit.

A

The pH decreases

the hydrogen ion concentration of
the solution increases by a factor of 10
(1 order of magnitude).

27
Q

What is a concentrated acid ? What is a dilute acid?

A

the amount of acid molecules in a given volume of solution

Concentrated acid has more moles of acid per unit volume than dilute (dilute refers to solutions of low concentrations)

28
Q

Is this the same as a strong and weak acid?

A

It is not the same

concentration is not the same thing as strength of an acid.

Strength refers to whether the acid is completely ionised in water (strong) or
only partially (weak
29
Q

how to carry out a titration 9

A
  1. Use a pipette & place 25 cm³ sodium hydroxide solution into a conical flask
  2. Add 5 drops of indicator phenolpthaleine) to the alkali in the conical flask -pink
  3. Place the conical flask on a white tile to see colour change clearly
  4. Fill a burette with sulfuric acid using funnel
  5. Add acid to the alkali until solution neutral
  6. colour change add drop by drop until neutral (swirl) -colourless
  7. read volume of acid added from the burette
  8. read at eyelevel with the surface of the liquid, bottom of meniscus
  9. Repeat until you achieve two concordant result
30
Q

what is 1dm³

A

1000cm

31
Q

What is electrolysis? 2

A

passing an electric current through ionic substances that are molten or in
solution to break them down into elements

ions are discharged (they lose/gain electrons) at electrodes

32
Q

What is an electrolyte?

A

liquid/solution which conducts electricity

33
Q

What is a cathode

What is
an anode?

A

Cathode is the negative electrode

anode is the positive electrode

34
Q

What occurs at the cathode

what occurs at the anode during electrolysis?

A

Reduction occurs at the cathode

Oxidation occurs at the anode

35
Q

why can molten ionic compouds be electolysed

A

the ions can be moved freesly and conduct electricity

36
Q

why is the elecrode made of inert material 3

A

so the material doesn’t react with the electrolyte -carbon replaced frequently
or platinum- unreactive metal

37
Q

In aqueous electrolysis, which element is discharged at the cathode?2

A

negative electrode cathode -hydrogen is produced unless the metal is less reactive than hydrogen.

This is because more reactive ions want to stay
within the solution.

38
Q

Oxygen is produced

at the anode unless what? 3

A

positive electrode anode,

OH- and halide ions (Cl-, Br-, I-) are present, then one
of the halide ions will be produced.

If no halide is present, oxygen is formed.

This happens because in the aqueous solution water molecules break down
producing H+ ions and OH- ions that are discharged

39
Q

Describe electrolysis of copper sulfate solution 2

A

cathode:
Cu²+ +2e- →Cu

anode:
4OH- → O₂ +2H₂0 +4e-

40
Q

describe electrolsis of sodium chloride

A

cathode
2H+ +2e- →H₂

anode
2Cl- → Cl₂ +2e-

41
Q

How is aluminium manufactured?

A

electrolysis of aluminium oxide and cryolite.

42
Q

Why electrolysis of aluminium expensive?

A

Lots of energy is needed to produce the current in electrolysis which makes this process expensive

43
Q

why a mixture is used as the electrolyte 3

A

it has a very high melting point

so it is mixed with cryolite to lower it

it reduces the amount of energy needed and saves money

44
Q

What are the half equations in

the extraction of aluminium?

A

Al³+ + 3 e− → Al (cathode)
reduction

2O₂− → O₂ + 4 e− (anode)
oxidation

Oxygen reacts with C of the anode producing CO2

45
Q

what is the overall equation for the electrolysis of aluminium oxide

A

2Al₂O₃+ 4Al + 3O₂

46
Q

Why is cryolite used in this

process?

A

lowers the melting point of aluminium oxide, reducing energy costs

47
Q

why the positive electrode anode must be continually

replaced.

A

the oxygen molecules produced at the anode react with the graphite (carbon) forming carbon dioxide gas

48
Q

How is oxidation and reduction defined in terms of electron transfer

A

oxidation- loss of electrons

reduction- gain of electrons

49
Q

Rules for electrolysis of ionic soloutions 4

A

cathode(negative)- metal produced if less reactive than hydrogen

hydrogen produced if the metal is more reactive than hydrogen

anode(positve)-If the negative ion is simple (eg Cl- or Br-), then that element is produced

If the negative ion is a complex ion (eg NO3-, SO42-, CO32-), then oxygen is produced from the hydroxide ion present instead.

Chemistry (14 decks)

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