unit 2 section 2 group 2 and group 7 elements

Question 1

how does Na react in water

Answer 1

Na reacts vigorously with cold water, it forms a molten ball and fizzes. it forms a strongly alkaline solution around ph-13-14

Question 2

how does mg reacts with water

Answer 2

Mg reacts slowly with water, you cannot see any reaction taking place. it forms a slightly alkaline solution around ph-10

Question 3

what is the formula for sodium reacting with water

Answer 3

2Na + 2H20 = 2NaOH +H2

Question 4

what is the reaction for magnesium and water

Answer 4

Mg + 2H20 = Mg(OH)2 + H2

Question 5

what is the reaction for magnesium and steam

Answer 5

Mg + H20(g) = MgO + H2

Question 6

what decided the solubility of the compound as you go down group 2

Answer 6

it is determined by the anion ( negative ion ) in the compound.

Question 7

describe the trend in solubility as you go down the hydroxides(OH-) compounds of group 2

Answer 7

the general trend is that the solubility increases as you go down group 2 due to the anion OH-

Question 8

describe the trend in solubility as you go down the sulfate(SO4,2-) compounds of group 2

Answer 8

the general trend is that the solubility of the sulfate compounds decreases as you go down group 2 because of the SO4,2- anion

Question 9

explain a medical use for barium sulfate

Answer 9

barium sulfate is insoluble, this is useful in the medicine. barium sulfate is opaque to x-rays which means it can be used to show the soft tissues such as the digestion system. it is given to the patient in the form of a barium meal. the barium meal is a suspension of the barium sulfate, the barium sulfate coats the tissue making it come up on the x-ray.

Question 10

what element is used to extract titanium

Answer 10

magnesium

Question 11

what process is used to purify the titanium chloride

Answer 11

fractional distillation

Question 12

what is the equation for the extraction of titanium

Answer 12

TiCl4(g) + 2Mg(l) = Ti(s) + 2MgCL2(l)

Question 13

what is the process called when removing sulfur dioxide from flue gases

Answer 13

wet scrubbing, it is the process is done by reacting it with an alkali( CaO & CaCO3 )

Question 14

explain the process of removing sulfur dioxide from flue gases

Answer 14

a slurry is made by mixing calcium carbonate or calcium oxide with water, it is then sprayed onto the flue gases. the sulfur dioxide reacts with the alkali slurry and produces a solid waste product, calcium sulfite

Question 15

what are the two equations for the removal of sulfur dioxide from flue gases with the two different alkalis

Answer 15

CaO(s) + 2H2O(l) + SO2(g) = CaSO3(s) + 2H20(l)

CaCO3(s) + 2H2O(l) + SO2(g) = CaSO3(s) + 2H2O(l) + CO2(g)

Question 16

give some other uses of group 2 element compounds

Answer 16

• neutralising acids
• Ca(OH)2 is used to in agriculture to neutralise acidic soils
  -Mg(OH)2 is used in indigestion tablets as an antacid ( neutralises excess stomach acids )

Question 17

explain what happens to the boiling point of halogens as you go down group 7

Answer 17

the boiling point increases as you go down group 7. this is because as you go down group 7 the size of the atom and Mr increases which means van der waals forces increase in strength which causes the boiling point to increase.

Question 18

explain what happens to the electronegativity of halogens as you go down group 7

Answer 18

the electronegativity decreases as you go down group 7. ( halogens are all highly electronegative elements ) this is because as you go down group 7 the size of the atom increase which means there is a further distance between the outer electron and the nucleus, larger ions attract electrons less than smaller ones, and there is also more shielding as there are more electron shells between the outer electron and the nuclues

Question 19

how do you identify which halogens or halides are present in a solution

Answer 19

a halogen will displace a halide from the solution if the halide is below it in the periodic table. this can be done by adding a few drops of aqueous halogen to a solution containing halide ions

Question 20

what is the equation for making bleach

Answer 20

2NaOH(aq) + Cl2(g) = NaClO(aq) + NaCl(aq) + H20(l)

Question 21

what is the oxidation state of a chlorate ion ( ClO-)

Answer 21

the oxidation state of cl in the ion is +1 and in the oxygen is -2 so the overall oxidation state of the ion is -1.

Question 22

what is the disproportionation reaction for chlorine and water

Answer 22

Cl2 + H2O = 2H+ + Cl- + ClO-

Question 23

how is water treated and what are some of the hazards with the treatment

Answer 23

drinking water is treated with chlorine or chlorate containing compounds in order to kill disease-causing microorganisms. however, chlorine gas is harmful if breathed in and liquid chlorine can cause severe on skin irritation or burns.

Question 24

what happens in the water treatment process the chlorine reacts with the organic compounds in the water

Answer 24

it reacts to the organic compounds to form chlorinated hydrocarbons and many of the chlorinated hydrocarbons are carcinogenic (cancer causing ), however this increased risk is small compared to the risks of untreated water.

Question 25

what happens to the reducing power of halides as you go down group

Answer 25

as you go down the group the reducing powers of halides increases, this is because as you go down the group the size of the atom increases, therefore the outer electron is further away from the nucleus and the amount of shells between the outer election and the nucleus. therefore, the force of attraction decreases which means the outer electron is more easily lost.

Question 26

what happens when halides react with concentrated sulfuric acid

Answer 26

when halides react with concentrated sulfuric acid they form hydrogen halides

Question 27

what is the general formula for halides reacting concentrated sulfuric acid

Answer 27

NaX + H2SO4 = NaHSO4 + HX

X represents the halide

Question 28

what happens when you react a strong halogen halide with sulfuric acid and what is the general formula for this

Answer 28

if the halide ion is strong enough it can reduce the concentrated sulfuric acid to water and sulfur dioxide.

2HX + H2SO4 = X2 + SO2 + 2H2O

X represents the halide ion

Question 29

how do you test for halides

Answer 29

first you add dilute nitric acid, in order to remove any ions that might interfere with the test. then you add a few drops of silver nitrate(AgNO3) and a precipitate will form ( sliver halide ). then to confirm your results you can test the solutions with different concentrations of ammonia

Question 30

what are the positive results when doing the test for halides.

Answer 30

fluorine - no precipitate
chlorine - forms white precipitate
bromine - forms cream precipitate
iodine - forms a yellow precipitate.

Question 31

how does chlorine, bromine and iodine react with different concentration of ammonia

Answer 31

chlorine - precipitate dissolve in dilute ammonia
bromine - precipitate dissolves in concentrated ammonia
iodide - precipitate insoluble in concentrated ammonia

Question 32

what are the tests for group 2 ions

Answer 32

flame test & sodium hydroxide or dilute sulfuric acid

Question 33

explain how you test for group 2 ions in the flame test

Answer 33

-dip a nichrome loop in concentrated HCl(too clean it ) and then dip it in the unknown compound.
- hold the nichrome loop in the clear blue part of the flame from the bunsen burner and observe the colour of the flame.

Question 34

what are the positive flame colours you will observe in the test for group 2 ions

Answer 34

Ca2+ =brick red flame
sr2+ =red flame
Ba2+ =pale green flame

Question 35

explain how they test for group 2 ions with sodium hydroxide

Answer 35

• add NaOH drop-wise to a test tube with the solution of the metal ion and observe the precipitate that forms
• keep adding NaOH in excess and record any observations that you see

Question 36

what are the positive results the test for group 2 ions with sodium hydroxide

Answer 36

OH - for Mg , Ca , Sr - forms a slight white precipitate and Ba has no change

in excess OH - for mg , it forms a white precipitate, Ca & Sr forms a slightly white precipitate and Ba has no change.

Question 37

what is the test for ammonia ions

Answer 37

damp piece of red litmus paper
positive - the paper will turn blue

Question 38

why does the litmus paper in the test for ammonia ions have to be damp

Answer 38

this is so that the NH3 gas can dissolve

Question 39

what is the test for ammonium ions

Answer 39

add warm dilute hydroxide ions
- if positive ammonia gas will be given off and it will turn damp red litmus paper blue

Question 40

explain the test for ammonium ions

Answer 40

• add some dilute sodium hydroxide to substance in a test tube and you gently heat it. if positive ammonia gas will be given of and you can test that it is ammonia by place a damp piece of red litmus paper above it and if it turns blue it is positive

NH4+(aq) + OH-(aq) = NH3(g) + H2O(l)

Question 41

Explain the test for sulfate ions

Answer 41

• add HCl and then barium chloride BaCl2 if a white precipitate forms then sulfate was present in original compound

Question 42

how do you test for carbonate ions

Answer 42

you add an acid such as HCl to the solution and a solution containing carbonate ions will fizz which you can then bubble it through lime-water and if the water turns cloudy then carbonate ions are present.