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Chemistry F321 > Redox and the Periodic Table > Flashcards

Redox and the Periodic Table Flashcards

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0
Q

What is a period?

A

A horizontal row of elements in the Periodic Table. Elements show trends in properties across a period.

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1
Q

What is a group?

A

A vertical column in the Periodic Table. Elements in the same group have similar chemical properties and their atoms have the same number of outer shell electrons, and the same type of orbitals.

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2
Q

What is periodicity?

A

A regular periodic variation of properties of elements with atomic number and position in the Periodic Table.

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3
Q

What is the most important factor across a period?

A

Nuclear charge.

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4
Q

What are the most important factors down a group?

A

Atomic radius and electron shielding.

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5
Q

What are the general properties of Group 2 elements?

A

Reasonably high melting and boiling points; light metals with low densities; form colourless compounds.

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6
Q

Why are the elements in Group 2 commonly called the alkaline earth metals?

A

They all have hydroxides that are alkaline.

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7
Q

How does reactivity change down Group 2?

A

It increases, as it gets easier to lose electrons, because of the decrease in ionisation energies.

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8
Q

Describe the reaction of a Group 2 elements with oxygen. What is the equation for the reaction of calcium with oxygen?

A

They react to form an ionic oxide, with the general formula MO. It is a redox reaction. They react vigorously.

2Ca(g) + O₂(g) → 2CaO(s)

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9
Q

Describe the reaction of Group 2 elements with water. What is the equation for the reaction of calcium with water?

A

They react to form hydroxides with the general formula M(OH)₂ and hydrogen gas. Magnesium reacts slowly with water, but they get more vigorous down the group.

Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)

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10
Q

What is an oxidation number?

A

A measure of the number of electrons that an atom uses to bond with atoms of another element.

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11
Q

What is the oxidation number of a uncombined element?

A

0

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12
Q

What is the oxidation number of combined oxygen?

A

-2

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13
Q

What is the oxidation number of combined hydrogen?

A

+1

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14
Q

What is the oxidation number of a simple ion?

A

The charge on the ion.

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15
Q

What is the oxidation number of combined fluorine?

A

-1

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16
Q

How do metals generally form ions?

A

By losing electrons with an increase in oxidation number to form positive ions.

17
Q

How do non-metals generally react?

A

By gaining electrons with a decrease in oxidation number to form negative ions.

18
Q

Are Group 2 oxides and hydroxides acids, bases, or alkalis?

A

Bases.

19
Q

What will you observe when a Group 2 oxide or hydroxide reacts with hydrochloric acid?

A

The solid oxide or hydroxide dissolve.

20
Q

What do the Group 2 oxides form when reacted with water? Give the equation for this with magnesium. What is the typical pH of this product?

A

A solution of the metal hydroxide.

MgO(s) + H₂O(l) → Mg(OH)₂(aq)

The typical pH is 10-12.

21
Q

What do the Group 2 hydroxides form when reacted with water? Give the equation for this with calcium.

A

They form alkaline solutions.

Ca(OH)₂(s) + aq → Ca²⁺(aq) + 2OH⁻(aq)

22
Q

How does the solubility of Group 2 hydroxides change down the group? How do the resulting solutions change down the group?

A

Solubility increases down the group. The resulting solutions are more alkaline down the group.

23
Q

Give two uses of Group 2 hydroxides.

A

1) Calcium hydroxide is used as ‘lime’ to neutralise acid soils.
2) Magnesium hydroxide is used in ‘milk of magnesia’ to relieve indigestion, by neutralising excess acid in the stomach.

24
Q

What is thermal decomposition?

A

The breaking up of a chemical substance with heat into at least two chemical substances.

25
Q

What is formed when Group 2 carbonates are decomposed by heat? Give the equation for magnesium. How does this change down the group?

A

They form a metal oxide and carbon dioxide gas.

MgCO₃(s) → MgO(s) + CO₂(g)

The carbonates become more difficult to decompose down the group.

26
Q

What are the states at RTP of Cl₂, Br₂ and I₂?

A

Gas, liquid and solid.

27
Q

What is the trend in boiling points of Cl₂, Br₂ and I₂? Explain this.

A

Increases down the group. This is because the number of electrons increases, so there are more van der Waals’ forces.

28
Q

What are the benefits of using chlorine in water treatment?

A

It kills bacteria in water supplies.

29
Q

What are the risks of using chlorine in water treatment?

A

Hazard of toxic chlorine gas; possible risk from formation of chlorinated hydrocarbons, which are suspected carcinogens.

30
Q

How does the reactivity of Group 7 elements change down a group?

A

It decreases.

31
Q

What is formed when Group 7 elements react with metals? Give an example.

A

Ionic halides with an X⁻ ion, i.e. NaCl.

32
Q

How do you test for halide ions?

A

1) Dissolve the halide substance in water.
2) Add an aqueous solution of silver nitrate, AgNO₃(aq).
3) Look at the colour of the precipitate formed (chloride is white, bromide is cream, iodide is yellow)

33
Q

What is a precipitation reaction?

A

The formation of a solid from a solution during a chemical reaction.

34
Q

What is a displacement reaction?

A

A reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter’s ions.

35
Q

What is disproportionation?

A

The oxidation and reduction of the same element in a redox reaction.

36
Q

What are the colours of chlorine, bromine and iodine in cyclohexane?

A

Chlorine: pale green
Bromine: orange
Iodine: violet

37
Q

What are the colours of chlorine, bromine and iodine in water?

A

Chlorine: pale green
Bromine: orange
Iodine: brown

38
Q

What is the trend in reactivity of Group 7 elements down the group, and why?

A

Decreases, because of the increasing atomic radius and electron shielding, and the decreasing ability to gain an electron into the p sub-shell to form a halide ion.

39
Q

How do you differentiate between halide ions with ammonia?

A

Chloride ions are soluble in dilute NH₃, bromide ions are soluble in concentrated NH₃, and iodide ions see insoluble in concentrated NH₃.

40
Q

Give the equation for the reaction of chlorine with water as used in water purification. What type of reaction is this?

A

Cl₂(aq) + H₂O(l) → HClO(aq) + HCl(aq)

Disproportionation reaction.

41
Q

Give the equation for the reaction of chlorine with cold, dilute aqueous sodium hydroxide, as used to form bleach. What type if reaction is it?

A

Cl₂(aq) + 2NaOH(aq) → NaCl(aq) + NaClO(aq) + H₂O(l)

Disproportionation reaction.

Chemistry F321 (5 decks)

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