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Chemistry > C4- Chemical Changes > Flashcards

C4- Chemical Changes Flashcards

1
Q

The lower the pH of a solution, the more _ it is

A

Acidic

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2
Q

The higher the pH of a solution, the more _ it is

A

Alkaline

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3
Q

What pH does a neutral substance have

A

7

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4
Q

What are the 2 way to measure pH

A

Using an indicator or a pH probe attached to a pH meter

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5
Q

What do acids and bases do

A

Neutralise each other

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6
Q

Acid + base →

A

Salt + water

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7
Q

H^+(aq) + OH^-(aq) →

A

H2O(l)

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8
Q

What are the 5 steps of the titration practical

A
  1. Using a pipette and pipette filler, add a set volume of the alkali to a conical flask.Add two or three drops of indicator too
  2. Use a funnel to fill a burette with some acid of known concentration. Make sure you do this BELOW EYE LEVEL- you don’t want to be looking up if some acid spills over. (Wear safety goggles) Record the initial volume of the acid in the bruette
  3. Using the burette, add the acid to the alkali a bit at a time- giving the conical flask a regular swirl. Go especially slowly when you think the end-point (colour change) is about to be reached
  4. The indicator changes colour when all the alkali has been neutralised, e.g phenolphthalein is pink in alkaline conditions, but colourless in acidic conditions
  5. Record the final volume on acid in the burette, and use it, along with the initial reading, to calculate the volume of acid used to neutralise the alkali
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9
Q

You need to repeat the titration experiment until your answers are within _cm^3 of each other

A

0.1

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10
Q

What colour do alkalis go when using litmus

A

Blue

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11
Q

What colour do alkalis go when using phenolphthalein

A

Pink

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12
Q

What colour do alkalis go when using methyl orange

A

yellow

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13
Q

What colour do acids go when using litmus

A

Red

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14
Q

What colour do acids go when using phenolphthealein

A

Colourless

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15
Q

What colour do acids go when using methyl orange

A

Red

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16
Q

HCI →

A

H^ +CI^-

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17
Q

HNO3→

A

H^+ + NO^-3

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18
Q

Strong acid: HCI→

A

H+ + CL-

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19
Q

Weak acid:CH3COOH →

A

H+ _ CH3COO-

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20
Q

pH is a measure of the concentration of _ _

A

Hydrogen ions

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21
Q

Factor H+ ion concentration changes by=

A

10^-x

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22
Q

Name three bases

A

Metal oxides ,metal hydroxides and metal carbonates

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23
Q

Acid + Metal Oxide →

A

Salt + Water

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24
Q

Acid + Metal Hydroxide →

A

Salt + Water

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25
Q

What do acids and metal carbonates produce

A

Carbon dioxide

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26
Q

List the reactivity series

A 
Potassium
Sodium
Lithium
Calcium
Magnesium
Carbon
Zinc
Iron
Hydrogen
Copper
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27
Q

Acid + Metal →

A

Salt + Hydrogen

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28
Q

Metal +Water →

A

Metal hydroxide + Hydrogen

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29
Q

What does oxidation mean

A

Gain of oxygen

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30
Q

What does reduction mean

A

Loss of oxygen

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31
Q

What Metals would be extracted by using electrolysis

A 
Potassium
Sodium
Lithium
Calcium
Magnesium
32
Q

What Metals would be extracted by reduction using carbon

A

Zinc
Iron
Copper

33
Q

What does OIL RIG stand for

A 
Oxidation
Is
Loss
Reduction
Is
Gain
34
Q

Are displacement reactions redox reactions

A

Yes

35
Q

Electrolysis means…

A

Splitting up with electricity

36
Q

Why are some elements extracted using electrolysis

A

They are more reactive than carbon

37
Q

Are metals attracted to negative or positive electrodes

A

Negative

38
Q

Are non-metals attracted to negative or positive electrodes

A

Positive

39
Q

What is an aqueous solution

A

A solution in which the solvent is water.

40
Q

What is a covalent bond

A

Covalent bonding results in the formation of molecules or giant structures.

41
Q

How many covalent bonds do hydrogen atoms make

A

One

42
Q

What is oxidation/reduction?

A

Oxidation - When a substance gains oxygen

Reducation - When a substance loses oxygen

43
Q

What is the reactivity series of
metals? What are the trends in
reactivities of metals in reactions
with acids/water?

A

The series shows the metals in order of their reactivity.
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

44
Q

What is a displacement reaction?

A

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

45
Q

How are unreactive metals found in Earth?

A

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

46
Q

How can metals less
reactive than carbon be
extracted?

A

Reduction with carbon. Carbon displaces the metal in a metal oxide - gets
oxidised to carbon oxides. Metal from the metal oxide gets reduced to the pure
metal.

47
Q

How are metals more reactive than carbon extracted?

A

By electrolysis

48
Q

How are oxidation and reduction defined in terms of electron

transfer?

A

Oxidation – loss of electrons

Reduction – gain of electrons

49
Q

What is the general equation for a
reaction between metals and
acids? What type of reaction is
this?

A

Metal + acid → salt + hydrogen

Redox reaction, also a displacement reaction

50
Q

Which metals in the reactivity series will react with acid?

A

Those above hydrogen

51
Q

What is the general equation for a

neutralisation reaction?

A

Base + acid → salt + water

52
Q

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

A

Metal carbonate + acid → salt + water + carbon dioxide

53
Q

What is the general equation for the reaction between metal

carbonates and acids?

A

Metal carbonate + acid → salt + water + carbon dioxide

54
Q

What is a redox reaction?

A

A reaction where both oxidation and reduction occurs

55
Q 
Explain in terms of gain or loss of
electrons which species has been
oxidised and which species has been
reduced when magnesium reacts with
hydrochloric acid
A

Magnesium has lost electrons and thus has been oxidised (Mg to Mg2+)
The hydrogen in HCl has gained electrons and thus has been reduced (H+ to H2)

56
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

57
Q

What do acids and alkalis produce in aqueous solutions?

A

Acids produce hydrogen ions, alkalis produce hydroxide ions

58
Q

What are bases, acids and

alkalis?

A

Bases are compounds that neutralise acids, acids produce hydrogen ions in
aqueous solutions, alkalis are soluble bases - produce hydroxide ions in aqueous
solutions

59
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

60
Q

State the general equation for a neutralisation

reaction in a short, ionic form.

A

H+ + OH− → H2O

61
Q

What is a strong acid? What is

a weak acid?

A

Strong acid is completely ionised in aqueous solution; weak acid is only partially
ionised in aqueous solution

62
Q

What happens to pH as
concentration of H+
increases?

A

The pH decreases

63
Q

What is a concentrated acid and
what is a dilute acid? Is this the
same as a strong and weak acid?

A
  • Concentrated acid has more moles of acid per unit volume than dilute (dilute
    refers to solutions of low concentrations)
  • 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)
64
Q

As the pH is decreased by one
unit, what change is seen in the
hydrogen ion concentration?

A

Increases by a factor of 10

65
Q 
Name the following salts:
LiNO3
, K2CO3
, MgBr2
, BaSO4
A

Lithium nitrate
Potassium carbonate
Magnesium bromide
Barium sulfate

66
Q

What is electrolysis

A

The passing of 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 to produce these

67
Q

What is an electrolyte?

A

The liquid/solution which conducts electricity

68
Q

What is a cathode and what is

an anode

A

Cathode is the negative electrode, anode is the positive electrode

69
Q

What occurs at the cathode
and what occurs at the anode
during electrolysis?

A

Reduction occurs at the cathode

Oxidation occurs at the anode

70
Q

In aqueous electrolysis, which
element is discharged at the
cathode? Oxygen is produced at
the anode unless what?

A

The less reactive element discharges at the cathode. Hydrogen is produced unless
there is a less reactive metal, in which case the said metal is produced. Oxygen is
produced at the anode unless the solution contains halide ions, in which case
halogen molecules are produced.

71
Q

How is aluminium manufactured?

Why is it expensive?

A

Aluminium is made through the electrolysis of aluminium oxide and cryolite.
Lots of energy is needed to produce the current in electrolysis which makes this
process expensive.

72
Q

What are the half equations in

the extraction of aluminium?

A

Al3+ + 3 e− → Al (cathode)
2 O2− → O2 + 4 e− (anode)
Oxygen reacts with C of the anode producing CO2
.

73
Q

Why is cryolite used in this

process?

A

It lowers the melting point of aluminium oxide, reducing energy costs

74
Q

What are the half equations in electrolysis of the aqueous

Na2SO4?

A

2 H+ + 2 e−→ H2 (cathode) 4 OH− → 2 H2O + O2 + 4 e-(anode)

75
Q

What are the half equations in
electrolysis of the molten and
aqueous KCl?

A 
K+ + e− → K (cathode)
2 Cl−→ Cl2 + 2 e− (anode)
2 H+ + 2 e− → H2
 (cathode)
2 O2− → O2+ 4 e− (anode), respectively
76
Q

What are the half equations in
electrolysis of the aqueous
CuBr2?

A

Cu2+ + 2 e− → Cu (cathode)

2 Br−→ Br2 + 2 e− (anode)

Chemistry (10 decks)

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