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Chemistry > Chemical Changes > Flashcards

Chemical Changes Flashcards

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?

A

The series which arranges metals in the decreasing order of reactivity.

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3
Q

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

A
  • Metals above hydrogen in reactivity series react with acid to produce hydrogen. - The higher the metal’s reactivity, the quicker and more vigorous it reacts with acid.
  • Metals below hydrogen don’t react with acids.
  • Not all metals above hydrogen react with water - mostly Group I and II metals. Aluminium is the borderline case.
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4
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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5
Q

How are unreactive metals found in Earth?

A
  • Unreactive metals (e.g., gold) are found in the Earth as the metal itself
  • Most metals are found as compounds that require chemical reactions to extract the metal.
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6
Q

How can metals less reactive than carbon be extracted? Explain your answer. (3)

A

Reduction with carbon. Carbon displaces the metal in a metal oxide (gets oxidised to carbon oxides) whilst the metal gets reduced to the pure metal.

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7
Q

How are metals more reactive than carbon extracted? (1)

A

By electrolysis

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8
Q

How are oxidation and reduction defined in terms of electron transfer? (1)

A

Oxidation – loss of electrons
Reduction – gain of electrons

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9
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, as well as a displacement reaction.

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10
Q

Which metals in the reactivity series will react with acid?

A

Those above hydrogen

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11
Q

What is the general equation for a neutralisation reaction?

A

Base + acid → salt + water

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12
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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13
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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14
Q

What is a redox reaction?

A

A reaction where both oxidation and reduction occurs.

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15
Q

Explain in terms of gain or loss of electrons which one has been oxidised and 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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16
Q

How is a soluble salt formed in a short way? (3)

A
  1. React the excess acid with some insoluble chemical (e.g. metal oxide)
  2. Filter off the leftovers
  3. Crystallise the product
17
Q

What do acids and alkalis produce in aqueous solutions?

A

Acids produce hydrogen ions, alkalis produce hydroxide ions

18
Q

What are bases, acids and alkalis? (3)

A

Bases: compounds that neutralise acids
Acids: substance that produces hydrogen ions in aqueous solutions
Alkalis: soluble base that produce hydroxide ions in aqueous solutions

19
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

20
Q

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

A

H⁺ + OH⁻ → H₂O

21
Q

What is a strong acid and weak acid?

A

Strong acid: an acid that is completely ionised (dissociated) in aqueous solution.
Weak acid: and acid that is only partially ionised (dissociated) in aqueous solution.

22
Q

What happens to pH as concentration of H⁺ increases?

A

The pH decreases.

23
Q

What is a concentrated acid and what is a diluted acid?

A

Concentrated acid: an acid that contains more moles of acid per unit volume in a solution.
Dilute acid: An acid that contains less mole of acid per unit volume in a solution.

24
Q

As the pH is increases by one unit, happens to the hydrogen ion concentration?

A

As the pH value increase by one unit, the hydrogen ion concentration decreases by a factor of 10.

25
Q

Name the following salts: LiNO3, K2CO3, MgBr2, BaSO4

A
  • Lithium nitrate
  • Potassium carbonate
  • Magnesium bromide
  • Barium sulfate
26
Q

What is electrolysis?

A

The method used to separate ionic compounds into their pure elements.

27
Q

What is an electrolyte?

A

The liquid/solution which conducts electricity

28
Q

What is a cathode and what is an anode?

A
  • Cathode is the negative electrode
  • Anode is the positive electrode
29
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
30
Q

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

A

Metal hydroxide + acid → salt + water

31
Q

Required Practical:
How is a soluble salt formed with a base/metal/carbonate, include reasons for certain steps? (9)

A
  1. Pour 40cm³ of dilute __ acid using a measuring cylinder into a beaker.
  2. Place the gauze on the surface of the tripod with the Bunsen burner underneath.
  3. Gently heat the acid until it is almost boiling to speed up the reaction and turn the bunsen burner off.
  4. Add a spatula of metal oxide into the acid and stir with a glass rod until a reaction occurs.
  5. Repeat step 4 until there is excess which shows that the acid and metal oxide have reacted.
  6. Pour the solution in the filter paper and funnel inside the conical flask.
  7. Repeat step 2 and place a beaker full of water and an evaporating basin with the solution on top of that.
  8. Gently heat the solution until crystals start to form and turn off the Bunsen burner.
  9. Set the solution in a cool area and when crystals have finished forming gently pat them dry using filter paper.
32
Q

Required Practical:
How is a soluble salt formed with an alkali? (11)

A
  1. Use the pipette and pipette filler to put the said volume of acid into the conical flask
  2. Stand the flask on a white tile.
  3. Clamp the burette using a clamp stand.
  4. At low eye level, pour a certain volume of the alkali into the burette using a funnel.
  5. Record the initial reading of alkali in the burette.
  6. Add 5 drops of indicator (phenolphthalein) to the conical flask.
  7. Slowly open the burette tap while swirling the conical flask.
  8. Add the acid drop-by-drop when the colour starts to change slightly.
  9. Close the burette when a permanent colour change occurs in phenolphthalein (from pink to colourless).
  10. Record the final reading of acid in the burette and calculate the titre.
  11. Repeat the process 2-3 times and calculate a mean removing any anomalies.

Chemistry (16 decks)

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