Elements of the sea

Question 1

Are nitrates & ethanoates soluble or insoluble?

Answer 1

All soluble

Question 2

Are sulphates all soluble/insoluble and what are the exceptions

Answer 2

All soluble except from- Ba, Pb and Ca

Question 3

Are halides soluble/insoluble and what are the exceptions?

Answer 3

All soluble apart from- Ag and Pb

Question 4

Are carbonates soluble/insoluble and what are the exceptions?

Answer 4

All are insoluble apart from - Na, K and NH4

Question 5

Are hydroxides soluble/insoluble and what are the exceptions?

Answer 5

All insoluble except from- Li, Na, K and Ca (sparingly soluble)

Question 6

Are oxides soluble/ insoluble and what are the exceptions?

Answer 6

All insoluble (Gp1 and 2 react with water to produce hydroxides)

Question 7

Write the ionic equation for:
Hydrochloric acid + sodium hydroxide —- sodium chloride + water

Answer 7

H+ + OH- —h20

Question 8

What are the two mains way to prepare soluble salts

Answer 8

Titration = acid + alkali
Acid + insoluble base= crystallisation

Question 9

How to test for insoluble salts

Answer 9

Precipitation reactions

Question 10

Deduce the oxidation numbers of each element in these compounds:

LiAlH4
Na2O2
NaclO4

Answer 10

Li -+1
Al- +3
H- -1

Na - +1
O- -1

Na- +1
Cl- +7
O- -2

Question 11

What is oxidation and reduction in redox reactions

Answer 11

Oxidation= gain of oxygen and loss of electrons (increase in oxidation number)

Reduction= loss of oxygen and gain of electrons (decrease in oxidation number)

Question 12

What is an oxidising agent?

Answer 12

An element or compound that has caused the oxidation of another, it accepts electrons so therefore is reduced.

Question 13

What is a reducing agent?

Answer 13

An element or compound that causes the reduction of another, it looses electrons and therefore is oxidised.

Question 14

Define electronegativity and state the most electronegative element

Answer 14

Electronegativity is a measure of the ability of an atom to attract the bonding pair electrons in a covalent to itself.

The most electronegative atom is Fluorine.

Question 15

State three physical properties of halogens

Answer 15

. Low melting and boiling points increases down group- increase in strength of intermolecular bonds
. Less volatile down the group
. solubility- non-polar molecules dissolve better in non-polar solvents

Question 16

State the colour and state ofF2, Cl2, Br2 and I2 at rtp.

Answer 16

F2- very pale yellow gas
Cl2- pale green gas
Br2- brown/red liquid
I2- shiny grey solid

Question 17

State the colour of Cl2, Br2 and I2 at non-polar solvents and water

Answer 17

Cl2- pale green, very pale green

Br2- orange, yellow/orange

I2- purple, brown/yellow

Question 18

State chemical properties of redox reactions in general

Answer 18

. Halogens are oxidising agents so are reduced and oxidising strength decreases down the group
. Halide ions are reducing agents so are oxidised and reducing strength increases down group

Question 19

Describe the method to react halogens with halide ions (redox)

Answer 19

1. Mix solution of halogen with halide ions
2. add organic (non-polar0 solvent (cyclohexane) and shake
3. The layers should separate
4. The upper layer will be the halogen dissolved in the organic solvent
5. use the colour as identification

Question 20

State the test for halide ions

Answer 20

1. acidify with HNO3
2. add aqueous AgNO3
3. Observe the colour of the precipitate
4. Add NH3 solution and shake

Question 21

State the four properties of hydrogen halides

Answer 21

1. covalent molecules
2. dissolve in water forms acidic solutions
3. Halide ions act as reducing agent
4. Reducing strength increases down the group

Question 22

Observation and equation of Sodium fluoride and sodium chloride

Answer 22

Observation: misty fumes of HF or HCL

Naf + H2SO4 -NaHSO4 + Hf
Nacl +H2SO4 -NaHSO4 +HCL

Question 23

Observation of NaBr and sulfuric acid and equation

Answer 23

Observation: Misty fumes of HBR and brown fumes (Br2)

2HBr + H2SO4 – SO2 + Br2 + 2H2O

Question 24

Reaction of NaI with sulfuric acid observation and equation

Answer 24

Observation: Misty fumes (HI) and a rotten egg smell

8HI + H2SO4– H2S + 4I2 + 4H2O

Question 25

What can be used as an alternative from sulfuric acid when reacted with hydrogen halides?

Answer 25

Phosphoric acid

Question 26

What happens at the anode?

Answer 26

Negative anions move towards the anode. Negative ions lose electrons forming atoms (oxidised).

Question 27

What happens at the cathode.

Answer 27

Positive cations more towards cathode. Positive ions gain electrons forming (reduced).

Question 28

State three properties of dynamic equilibrium

Answer 28

1. rates of forwards= rates of backwards reaction 2. concentrations of reactants and products remains constant 3. only exists in closed systems

Question 29

What is Le Chatelier's principle?

Answer 29

The position of equilibrium will shift so as to minimise the effect of any change in conditions.

Question 30

Summarise the effect of temperature on equilibrium

Answer 30

If forwards is exothermic= an increase of temp will shift it to left, decrease in temp will shift to right If forwards is endothermic= an increase in temp will shift to right, decrease in temp will shift left

Question 31

Summarise the effect of pressure on equilibrium

Answer 31

If forwards produces more moles of gas: shifts to left with less moles when increased pressure, decreased pressure will shift to right with more moles Opposite if forward produces less moles.

Question 32

How to test for carbonates

Answer 32

Add an acid and if there is effervescence then CO32- ions are present. To prove this bubble it through limewater and it'll turn cloudy.

Question 33

How to test for sulphate ions

Answer 33

Add nitric acid and barium nitrate solution. A white precipitate will form.

Question 34

How to test for halide ions

Answer 34

Add nitric acid and silver nitrate then a coloured precipitate will determine which halide is present. Then add ammonia to determine further.

Question 35

How to test for ammonium ions

Answer 35

Add sodium hydroxide and warm the mixture. Test it with red damp litmus paper and it'll turn blue.