Topic 4

Question 1

What is the definition of first ionisation energy

Answer 1

The energy required to remove an electron from each atom in one mole of atoms in a gaseous state

Question 2

What is the trend in ionisation energy down group two

Answer 2

The ionisation energy decreases

Question 3

Why does the ionisation energy down group 2 decrease

Answer 3

Although the nuclear charge increase so the force of attraction for the electron being removed increases
However, as each quantum shell increases down the group, energy of the outermost electron increases
As the number of filled inner shells increases, there is a force of repulsion on the electron being removed increases

Question 4

What is the trend in reactivity down group two

Answer 4

The reactions become more vigorous and the elements are more reactive down group two

Question 5

What occurs when magnesium burns in air

Answer 5

There is a bright white flame and the formation of a white solid

Question 6

Why does the reactivity increase down group two

Answer 6

Because the ionisation energy increases down the group making it easier for the atom to loose electrons and become a 2+ ion

Question 7

What is the general equation for when a group two element reacts with oxygen and water vapour

Answer 7

2M(s) + O2 —-> 2MO(s)

Question 8

How does magnesium react with water

Answer 8

There is a very slow reaction that does not proceed completely

Question 9

What is the general equation for a group two element reacting with water

Answer 9

M(s) + 2H2O(L) ——> M(OH)2(aq) + H2(g)

Question 10

What is the general equation for the reaction of chlorine with group 2 elements

Answer 10

M(s) + Cl(g) ——> MCl(s)

Question 11

What is the general equation for the reaction of group two oxides with water

Answer 11

MO(s) + H2O(L) ——> M(OH)2(aq)

Question 12

What is the trend in the solubility of hydroxides of group 2 elements

Answer 12

The solubility increases down the group making it

Question 13

What is the trend in solubility of group two sulfates

Answer 13

Magnesium sulfate is classed as soluble
Calcium sulfate is classed as slightly soluble
Strontium and barium sulfate are classed as insoluble

Question 14

How do hydroxides of group 2 elements reacts with dilute acids

Answer 14

They form salts and water
Described as a neutralisation reaction
A white solid reacts to form a colourless solution
The reaction is exothermic

Question 15

What is the general equation for the reaction between a hydroxide of a group 2 element and dilute acid

Answer 15

M(OH)2 + 2HCl ——> MCl2 + 2H2O

Question 16

Define thermal stability

Answer 16

How stable a compound is when heated (how much it decomposes)

Question 17

How can the thermal stability of nitrates be observed

Answer 17

When they are heated they decompose into nitrates or oxides and give off nitrogen dioxide (brown fumes) or oxygen. Therefore, brown fumes indicate more decomposition and no brown fumes indicates less decomposition.

Question 18

What forms when group two oxides are reacted with water

Answer 18

An alkaline solution forms

Question 19

What is the test for hydrogen

Answer 19

A glowing splint will cause a squeaky pop

Question 20

What is the test for oxygen

Answer 20

A glowing splint will re-light

Question 21

What is the test for chlorine

Answer 21

Blue litmus paper will red and then bleach

Question 22

What is the test for CO2

Answer 22

It will turn lime water cloudy

Question 23

What is the test for carbonate ions

Answer 23

Ad an acid and the gas produced will turn lime water cloudy

Question 24

What is the test for ammonia gas

Answer 24

Ad NaOH and It will turn moist red litmus paper blue

Question 25

What is the test for ammonium ions

Answer 25

Ad NaOH warm the mixture and it will produce ammonia which will turn red litmus paper blue

Question 26

What is the test for sulfate ions

Answer 26

Add HCl and BaCl2 ions which form a precipitate

Question 27

What is the method for a flame test

Answer 27

Clean platinum wire Hold it in the edge of a blue flame until there is no colour Dip the cooled wire in conc HCl to remove any contaminants Pick up one crystal o with the wire Hold in the edge of the blue flame

Question 28

What are the flame test colours for group one ions

Answer 28

Li+ = red Na+ = yellow/orange K+ = lilac Rb+ = red/purple Cs+ = blue/violet

Question 29

What are the flame test colours for group two ions

Answer 29

Be 2+ = no colour Mg2+ =no colour Ca2+ = brick red Sr2+ = crimson red Ba2+ = apple green

Question 30

What causes a flame test colour

Answer 30

The metal absorbs the heat energy and it excites the electrons to move from their “ground” orbit to a higher energy orbit The electrons will fall back down to their ground level orbit and emit the difference in energy between the two levels as photon If the energy emitted has a wavelength on the visible spectrum we will see a colour Different metals will have different “gaps” and therefore will emit different colours

Question 31

What causes a flame test colour

Answer 31

The metal absorbs the heat energy and it excites the electrons to move from their “ground” orbit to a higher energy orbit The electrons will fall back down to their ground level orbit and emit the difference in energy between the two levels as photon If the energy emitted has a wavelength on the visible spectrum we will see a colour Different metals will have different “gaps” and therefore will emit different colours

Question 32

Explain the trend in boiling points for group seven elements

Answer 32

The boiling point and melting point increases down the group Because they form London forces and down the group the number of electrons increase This means that more London forces can form and more energy is required to overcome the London forces

Question 33

What is the physical states at room temperature of group seven elements

Answer 33

Fluorine + chlorine are gas Bromine is liquid Iodine is a solid

Question 34

Wxplain the trend in reactivity down group seven

Answer 34

They all gain one electron when they react Down the group the ionic radii increase This means there are more shells and more shielding Less attraction to electrons Harder to gain one electrons making it less reactive down the group

Question 35

Explain the trend of ionisation energy down group seven

Answer 35

All gain 1 electron when they react Down the group atomic radius increases More shielding Less attraction to electrons Harder to gain an electron – higher ionisation energy down the group the

Question 36

What is a displacement reaction

Answer 36

When a more reactive element takes the place of a less reactive element from its salt

Question 37

What are the generalisations of reactions between group 1/2 elements and group 7 elements

Answer 37

Most vigorous with elements at the bottom of group one and two and the top of group seven The products are ionic salts - normally white All the reactions involve an electron transfer to the halogen (group 7= oxidising reagent)

Question 38

Why should you ad an organic solvent (such as cyclohexane) after a redox reaction in group seven

Answer 38

Halogens are more soluble in cyclohexane than water Halogen dissolves in upper layer where it’s colour can be more easily seen This is because the reaction can be indicated by a colour change but interpreting colour changes is difficult due to the similarities of colours and the variation in colour with concentration

Question 39

How does chlorine react with water

Answer 39

There is a disproportional reaction Chlorine is reduced to form HCl and oxidised to form HClO

Question 40

Why are metal carbonates with a larger metal more stable

Answer 40

Because there charge is more distributed They are less likely to distort/ polarise the carbonate ion So the C-O bond within the carbonate ion is not weakened

Question 41

Why are group 1 carbonates more thermally stable than group two

Answer 41

Group two produce ions with a higher charge Group two polarises the carbonate ion more So the C-O bond is weakened more

Question 42

Explain the trend in reactivity down group 7

Answer 42

The reactivity decreases down group seven Because their electronegativity decreases down the group Most of their reactions involves acting as a oxidising agent and gaining electrons to form negative ions of the delta negative part of a polar molecule

Question 43

How does chlorine react with cold dilute aqueous sodium hydroxide

Answer 43

Disproportionation reaction Forms NaCl (chlorine being reduced) and NaClO (chlorine being oxidised) and water The NaCl is a bleach

Question 44

How does chlorine react with hot alkali (sodium hydroxide)

Answer 44

Disproportionation reaction occurs Forms NaCl (reduction) and NaClO3 (oxidation) NaClO3 is used in bleaching and weed killer

Question 45

Why is a platinum wire used in a flame test

Answer 45

It produces no colour when in a flame It is unreactive/ inert

Question 46

Why is HCl used in a flame test

Answer 46

To clean the wire To moisten the wire to allow it to pick up the solid salts

Question 47

What occurs when magnesium nitrate is heated

Answer 47

Brown gas is formed The solid dissolves A white solid forms Precipitate on the sides of the tube

Question 48

How do you test / compare the rate of decomposition of metal carbonates

Answer 48

Use the delivery tube to collect bubble gas into limewater Compare the time taken for limewater to turn cloudy

Question 49

How does sodium chloride react with sulfuric acid

Answer 49

Forms steamy acidic fumes