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Chemistry Leaving Cert > Oxidation and Reduction > Flashcards

Oxidation and Reduction Flashcards

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1
Q

What is oxidation?

A

The addition of oxygen, the loss of electrons and the increase in oxidation number

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2
Q

What is reduction?

A

A loss of oxygen, gain of electrons and decrease in oxidation number

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3
Q

What does an oxidising agent do?

A

causes oxidation and is itself reduced

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4
Q

What does a reducing agent do?

A

causes reduction and is itself oxidised

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5
Q

What is the most abundant element on the earths crust and in the human body?

A

Oxygen

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6
Q

What does oxygen combine with?

A

the vast majority of other elements

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7
Q

What is oxygen involved in?

A

some of the most important chemical reactions - burning, respiration, rusting

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8
Q

What did oxidation used to be defined as and give an example?

A

the addition of oxygen to a substance e.g. C + O2 -> CO2

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9
Q

What did reduction used to be defined as?

A

the removal of oxygen

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10
Q

Before the discovery of electrons, what were reactions that involved the addition of oxygen to a substance described as?

A

oxidation reactions

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11
Q

What was removing oxygen from a substance previously described as? Why?

A

a reduction reaction as the mass to the substance got smaller due to the oxygen being removed

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12
Q

What did scientists notice after the discovery of the electron?

A

Scientists examined reactions more closely and noticed that many chemical reactions involved the transfer of electrons. One substance lost electrons while another gained electrons.

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13
Q

What did the transfer of electrons involve?

A

One substance losing electrons while another gained electrons.

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14
Q

What is oxidation?

A

When an element loses electrons

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15
Q

What is reduction?

A

Reduction is when an element gains electrons

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16
Q

What do we use to remember oxidation and reduction?

A

OIL RIG

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17
Q

What does OIL RIG stand for?

A

Oxidation Is Loss, Reduction Is Gain

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18
Q

Write down a formula to show oxidation and reduction explaining what has been oxidised and why

A

Zn + Cu2+ -> Zn2+ + Cu (remember Zn is more positive so it lost negatives so it has been OXIDISED not REDUCED)

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19
Q

When do oxidation and reduction occur?

A

At the same time

20
Q

If one element loses electrons, what happens to another element?

A

It gains electrons

21
Q

Give two examples of REDOX reactions

A
  1. MgO -> Mg2+ + O2-

2. Zn + Cu2+ -> Zn2+ + Cu

22
Q

Give an example of a REDOX reaction and explain

A

MgO -> Mg2+ + O2-
In the above example we can see that the Mg atom loses 2e to become the Mg2+ ion. The O atom gains 2e to become the O2- ion.

23
Q

Name the metals more reactive than hydrogen from most reactive to least reactive

A

Potassium (K), Sodium (Na), Calcium (Ca), Magnesium (Mg), Aluminium (Al), Zinc (Zn), Iron (Fe), Tin (Sn), Lead (Pb) and then |Hydrogen| |H|

24
Q

Name the metals less reactive than hydrogen from most reactive to least reactive

A

Copper (Cu), Mercury (Hg), Silver (Ag), Gold (Au)

25
Q

What is electrolysis?

A

The use of electricity to bring about a chemical reaction in an electrolyte

26
Q

What is an electrolyte?

A

An electrolyte is a compound which when molten or dissolved in water will conduct an electric current

27
Q

What is the conduction of electricity due to?

A

the presence of ions

28
Q

What is the electrochemical series?

A

a list of elements in order of their standard electrode potential (reactivity - how easily they lose electrons)

29
Q

What are electrodes?

A

The two rods that dip into the electrolyte and make electrical contact with it

30
Q

What are the two types of electrodes?

A

Inert (do not react with electrolyte) and Active (react with electrode)

31
Q

What are examples of inert and active?

A

inert -> graphite and platinum

active -> copper and iron

32
Q

how is the electrochemical series organised?

A

top of the list readily lose electrons

bottom = unreactive

33
Q

are the electrodes positive or negative?

A

One electrode is positive and the other is negative

34
Q

is a cathode negative or positive?

A

negative

35
Q

is an anode positive or negative?

A

positive

36
Q

how do we remember the charge of cathodes and anodes?

A

CNAP

37
Q

What does CNAP stand for?

A

Cathode, Negative, Anode, Postive

38
Q

What happens to electrons in the electrodes?

A

The battery “pumps” electrons to the negative electrode where they are gained by some species and carried to the positive electrode where they are lost

39
Q

oxidation at anode or cathode?

A

anode

40
Q

reduction at anode or cathode?

A

cathode

41
Q

What happens in electrodes connected to a DC current?

A

Positive ions move to negative electrode and gain electrons

Negative ions move to positive electrode and lose electrons

42
Q

anion positive or negative?

A

negative

43
Q

cation positive or negative?

A

positive

44
Q

Write the equations for when an electrical current passes through a solution of potassium iodide using inert electrodes.

A

Anode (+): 2I- -> I2 + 2e-
(loss of electrons - oxidation)
Cathode (-): 2H2O + 2e- -> H2 + 2OH-
(gain of electrons - reduction)

45
Q

Do K+ ions gain electrons at cathode?

A

no

46
Q

does K+ + e- -> K takes a lot of energy?

A

yes

47
Q

is K+ a spectator ion?

A

yes

Chemistry Leaving Cert (10 decks)

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