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GCSE Chemistry > Chemical Reactions > Flashcards

Chemical Reactions Flashcards

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1
Q

What does the law of conservation of mass state?

A

In a chemical reaction, no matter is destroyed or created

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2
Q

What is a chemical change?

A

A rearrangement of the atoms in the reactants, to form the products

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3
Q

Why may the balance reading for the products be more than the reading for the reactants?

A

Gas from the air reacted with the reactants

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4
Q

What is the formula that links mass, moles, and Mr?

A

moles = mass/Mr

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5
Q

What is the limiting reactant?

A

It all reacts and limits how much product can be formed

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6
Q

What does it mean for a reactant to be ‘in excess’?

A

It does not all react, and has no affect on the amount of product formed

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7
Q

If the reactant molecules in a reaction have more energy in their chemical bonds than the product molecules, will energy be absorbed or released overall?

A

released

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8
Q

What is an exothermic reaction?

A

A reaction that releases thermal energy to the surroundings

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9
Q

What is an endothermic reaction?

A

A reaction that takes in thermal energy from the surroundings

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10
Q

If an exothermic reaction occurs in a closed container, what would happen to the temperature inside the container?

A

The temperature would increase

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11
Q

If an endothermic reaction occurs in a closed container, what would happen to the temperature inside the container?

A

The temperature would decrease

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12
Q

what is activation energy?

A

the minimum amount of energy the reactant particles require in order to collide successfully with each other and react.

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13
Q

On reaction profile diagrams, what is the activation energy?

A

the increase in energy from the reactants to the peak of curve.

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14
Q

Does breaking bonds release energy or require energy?

A

require

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15
Q

Is breaking bonds exothermic or endothermic?

A

Endothermic

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16
Q

What is bond energy?

A

the amount of energy required to break one mole of a particular covalent bond.

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17
Q

Is forming a bond an exothermic or endothermic process?

A

exothermic

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18
Q

How do you calculate the overall enthalpy change of a reaction?

A

(energy of) bonds broken - (energy of) bonds formed

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19
Q

What type of reaction produces a negative energy change?

A

An exothermic reaction

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20
Q

What does the pH scale measure?

A

acidity or alkalinity of a solution

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21
Q

What pH does stomach acid typically have?

A

about 2

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22
Q

What are 2 ways to measure the pH of a solution?

A

Chemical indicator

pH probe

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23
Q

What ion is responsible for making a solution alkaline when it’s dissolved in it?

A

OH -

24
Q

Which products are formed when an acid reacts with a metal oxide?

A

a salt and water

25
Q

What type of reaction is it when an acid and a base react together?

A

Neutralisation reaction

26
Q

Which products are formed when an acid reacts with a metal hydroxide?

A

a salt and water

27
Q

Which products are formed when an acid reacts with a metal carbonate?

A

a salt, water and carbon dioxide

28
Q

How do you obtain soluble salt crystals from an acid-base reaction?

A

1)Place dilute acid in a beaker and heat gently.
2)Add the solid base bit by bit until it stops reacting, which means it’s in excess.
3)Isolate the salt solution by filtering out the excess solid base using filter paper and a funnel.
4)Heat the salt solution gently in a water bath until crystals start to form.
5)Let the solution cool further, which will cause more crystals to precipitate.
6) Filter out the soluble salt crystals using filter paper and funnel.

29
Q

What does it mean when an acid ionises?

A

when the acid molecules are added to water, they split apart

30
Q

Whats the difference between a strong and a weak acid?

A

Strong acids ionise completely, whereas weak acids only partially ionise.

31
Q

What are 3 strong acids?

A

Nitric acid

Sulfuric acid

Hydrochloric acid

32
Q

is the ionisation of weak acids reversible?

A

yes

33
Q

What are 3 weak acids?

A

carbonic
ethanoic
citric

34
Q

As the concentration of hydrogen ions in a solution increases, what happens to the pH?

A

The pH decreases

35
Q

A solution decreases from pH 6 to pH 5.
By what factor has the concentration of hydrogen ions increased?

A

x10

36
Q

With respect to electrons, reduction is:

A

The gain of electrons

37
Q

With respect to electrons, oxidation is:

A

the loss of electrons

38
Q

What is a spectator ion?

A

an ion that doesn’t take part in the reaction and so keeps the same charge

39
Q

An electrolysis cell has two electrodes. What is the name of the positive electrode?

A

anode

40
Q

An electrolysis cell has two electrodes. What is the name of the negative electrode?

A

cathode

41
Q

What is the name of the liquid the electrodes are put in?

A

electrolyte

42
Q

In electrolysis, which direction do the electrons travel?

A

Anode ➔ Cathode

43
Q

What does the term ‘inert’ mean?

A

unreactive

44
Q

In the electrolysis of molten lead bromide, what is the product at the anode?

A

bromine

45
Q

In electrolysis, why does the compound you’re trying to separate need to be molten or dissolved?

A

So that the ions are free to move around (and go to their respective electrode)

46
Q

Which 2 chemical processes are used to extract metals from their ores?

A

reduction with carbon and electrolysis

47
Q

What is electrolysis?

A

the splitting of an ionic compound using electricity

48
Q

Why is electrolysis not used to extract all metals?

A

Electrolysis is expensive because it requires a large amount of electricity

49
Q

When should a metal be extracted by carbon reduction?

A

When the metal is less reactive than carbon

50
Q

Why is electrolysis used to extract aluminium from its ores?

A

it is more reactive than carbon

51
Q

What is the name of the substance that is mixed with aluminium oxide to lower its melting point?

A

cryolite

52
Q

In the electrolysis of a solution, which two ions are present from the water molecules themselves?

A

H+ OH-

53
Q

What is the rule to determine which ion get discharged at the cathode in aqueous electrolysis?

A

the ions of the least reactive metal will be discharged (usually copper or hydrogen)

54
Q

What is the rule to determine which ion get discharged at the anode in aqueous electrolysis?

A

If halide is present, it gets discharged, otherwise hydroxide gets discharged

55
Q
A

GCSE Chemistry (7 decks)

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