Redox And Groups 2&7

Question 1

The oxidation number of elements

Answer 1

0

Question 2

Oxidation numbers of group 1 and 2

Answer 2

1 and 2

Question 3

Oxidation number of fluorine

Answer 3

-1

Question 4

Oxidation number of oxygen

Answer 4

-2 unless attached to itself then it’s 0 or fluorine when it becomes positive

Question 5

Oxidation number of group three elements onwards

Answer 5

Up to its group number

Question 6

Oxidation number of hydrogen

Answer 6

-1 when attached to metals or +1 when attached to more electronegative non metals

Question 7

Oxidation

Answer 7

The addition of oxygen
The loss of electrons
An increase in oxidation number

Question 8

Reduction

Answer 8

The removal of oxygen
The gain of electrons
A decrease in oxidation number

Question 9

Redox

Answer 9

A reaction with both reduction and oxidation

Question 10

Halogens- trend in boiling point

Answer 10

Increases down the group as there are more electrons so stronger London forces. More energy is required to break the intermolecular force

Question 11

Halogens- shell arrangement

Answer 11

2 electrons on the outer S-sub shell and 5 in the outer P sub shell.

Question 12

What happens to halogens in a reaction

Answer 12

They are reduced, gaining one electron to form a 1- ion

Question 13

Halogens halide displacement reaction

Answer 13

Done to show that reactivity decreases down the group. A solution of each halogen is added to an aqueous solution of the other halide. If the halogen is more reactive then the ion then a reaction takes place and the halogen displaces the halide from the solution and the solution changes colour

Question 14

Halogen colour in water

Answer 14

Cl2- pale green
Br2-orange
I2- brown

Question 15

Halogen colour in cyclohexane

Answer 15

Cl2- pale green
Br2-orange
I2-violet

Question 16

Why would you add cyclohexane in halogen reactions

Answer 16

As in water iodine and bromine are a similar colour so it helps to tell them apart. When a reaction has occurred the solution turns the colour of the displaced halide

Question 17

Halogen reactivity trend

Answer 17

They get less reactive down the group as atomic radius increases, more inner shells so shielding increases, so less nuclear attraction to capture an electron from another species

Question 18

Disproportionation

Answer 18

A redox reaction in which the same element is both oxidised and reduced

Question 19

The reaction of chlorine with water

Answer 19

Cl2+H2O—>HClO+HCL
0 +1 -1
HClO and HCl are both acids, the bacteria is killed by chlorine acid and chlorate ions (ClO-). Chlorine is used in water purification

Question 20

Chlorine with cold, dilute aqueous sodium hydroxide

Answer 20

Cl2+2NaOH——>NaClO+NaCl+H2O
0 +1 -1

Bleach is formed by reacting chlorine with cold dilute aqueous sodium hydroxide as more ClO- ions are formed

Question 21

Ionisation energy group 2

Answer 21

The ionisation energy decreases down the group because the attraction between the nucleus and the outermost electron decreases due to shielding and an increase in atomic radius which overcomes the increase in nuclear charge.

Question 22

Group 2 reactivity

Answer 22

They need to loose two electrons which requires the input of the first two ionisation energies. As ionisation energy decreases down the group reactivity increases as less energy is needed to loose the 2 elections which are needed for a reaction to take place. They become stronger reducing agents down the group.

Question 23

Group 2 oxides with water

Answer 23

They release OH- ions and form alkaline solutions of metal hydroxides. CaO+H2O—> Ca+2+2OH- group 2 hydroxides are only slightly soluble in water when the solution is saturate any further metal and hydroxide ions will form a solid participate Ca+2+OH- —> Ca(OH)2

Question 24

Benefits of Chlorine use

Answer 24

Kills bacteria so stops water contaminated diseases such as typhus and makes it safe to drink. Benefits outweigh disadvantages

Question 25

disadvantages of Chlorine use

Answer 25

Is a respiratory irritant in small quantities and can be fatal in large quantities. Can react with organic hydrocarbons such as methane from dying vegetation to form chlorinated hydrocarbons which is a carcinogenic.

Question 26

Group 2 elements shell arrangements

Answer 26

S2 arrangement, they loose these electrons in redox reactions to form +2 ions.

Question 27

Redox reactions with oxygen group2

Answer 27

Form metal oxides
2Mg+O2–>2Mgo. the metal increases by 2 oxidation numbers the oxygen decreases by 2. Reaction mre vigorous down the group

Question 28

Redox reactions with water group 2

Answer 28

Sr+2H2O–>Sr(OH)2+H2.
Water and magnesium react very slowly but reactions become more vigorous down the group. Hydrogen gas and an alkaline hydroxide is formed.

Question 29

Group2 redox reactions change in oxidation number

Answer 29

the group 2 metal increases by 2, the hydrogen which forms H2 decreases by 1 each, the 2 H forming X(OH)2 do not change.

Question 30

Redox reactions with acid

Answer 30

metal +acid –> salt +hydrogen. Mg increases by 2 hydrogen decreases by 1.

Question 31

solubility trend in group 2 hydroxides

Answer 31

the solubility of the hydroxides in water increases down the group so resulting solutions contain more OH ions so are more alkaliney

Question 32

group 2 oxide which neutralises acidic soil

Answer 32

CaOH2

Ca(OH)2+2H+–>Ca+2+2H2O

Question 33

group two oxides to treat indigestion

Answer 33

Mg(OH)2 and CaC03 are used as antacids
Mg(OH)2+2HCl–>MgCl2+2H2O
CaCo3+2HCl–>CaCl2+H2O+CO2

Question 34

Reaction of group 2 metals with water

Answer 34

Reaction is more vigorous down the group. Hydrogen gas is released. A white precipitate will form, down the group it becomes more soluble so it might dissolve nd there wont be a precipitate.