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Chemistry GCSE > C5. Chemical Changes > Flashcards

C5. Chemical Changes Flashcards

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1
Q

What is oxidation/reduction?

A

Oxidation - When a substance gains oxygen
Reduction - When a substance loses oxygen

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2
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 the 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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3
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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4
Q

How are unreactive metals found in Earth?

A

In their natural state

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5
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

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6
Q

How are metals more reactive than carbon extracted?

A

By electrolysis

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7
Q

How are oxidation and reduction defined in terms of electron transfer?

A

Oxidation - loss of electrons
Reduction - gain of electrons

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8
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

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9
Q

Which metals in the reactivity series will react with acid?

A

Those above hydrogen

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10
Q

What is the general equation for a neutralisation reaction?

A

Base + acid –> salt +water

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11
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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12
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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13
Q

What is a redox reaction?

A

A reaction where both oxidation and reduction occurs

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14
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)

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15
Q

How is a soluble salt formed?

A

a) React the excess acid with some insoluble chemical
b) Filter off the leftovers
c) Crystallise the product

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16
Q

What do acids and alkalis produce in aqueous solutions?

A

Acids produce hydrogen ions, alkalis produce hydroxide ions

17
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

18
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

19
Q

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

A

H+ + OH- —> H₂O

20
Q

What is a strong acid and weak acid?

A

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

21
Q

What happens to pH as concentration of H+ increases?

A

The pH decreases

22
Q

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

A

Concentrated acid has more moles of acid per unit volume than 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)

23
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

Chemistry GCSE (10 decks)

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