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Chemistry > Unit 2: Section 2: Group 2 and Group 7 Elements > Flashcards

Unit 2: Section 2: Group 2 and Group 7 Elements Flashcards

1
Q

Where in the periodic table are the alkaline earth metals

A

In the s block of the periodic table

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2
Q

Explain the trend in the atomic radius when you go down a group on the periodic table

A

The atomic radius gets larger because extra electron shells are added as you go down the group

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3
Q

Explain the trend in first ionisation energy as you go down group 2

A

Decreases as you go down the group
Each element as you go down group 2 as another electron shell compared to the one above it
This means more shielding and the outer electrons are farther away from the nucleus

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4
Q

Explain the trend in melting point in the group 2 elements and what is an anomaly to this trend

A

Generally decrease down the group
The metal ions get bigger but the number of delocalised electrons doesn’t change
The larger the ionic raidus the further away the electrons are from the nuclei - so it takes less energy to break the bonds meaning the melting point decreases
Magnesium is much lower than the other elements because of the crystal structure

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5
Q

What happens when the Group 2 elements react with water

A

Oxidised from a state of 0 to 2+

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6
Q

What happens when Group 2 metal react with water

A

They give a metal hydroxide and an hydrogen

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7
Q

What are the trends of reactivity when you go down the Group 2 elements

A

It increases

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8
Q

Explain the solubility of Group 2 compounds

A

If the compound contain one negative ion than the elements increase in solubility down the group - the opposite is true if the compound contain doubly charged negative ions

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9
Q

What is the norm of solubility in water for the sulfates and what is the exception

A

Normally soluble but barium sulfate is insoluble

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10
Q

What is the test for sulfate ions

A

Add dilute hydrochloric acid and then barium chloride to a solution containing sulfate ions then a white precipitate of barium sulfate is formed

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11
Q

How can barium sulfate be useful in medicine

A

Used in barium meals to diagnoes problems with oesophague, stomach or intestines
The barium sulfate in the meal coats the tissues making them show up on the X-rays

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12
Q

What is the main titanium ore

A

Titanium (IV) oxide (TiO2)

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13
Q

How is the titanium extracted from the main titanium ore

A

It is first converted from titanium (IV) oxide (TiO2) to titanium (IV) chloride (TiCl4) by heating it with carbon in a stream of chlorine gas
The titanium chloride is then purified by fractional distillation before being reduced by magnesium in a furnace at almost 1000 degrees celcius

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14
Q

What is the equation for the reduction of titanium chloride using magnesium

A

TiCl4 (g) + 2Mg (l) -> Ti (s) + 2MgCl2 (l)

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15
Q

Explain the process of wet scrubbing

A

Calcium oxide and calcium carbonate is mixed into something called a slurry
It is then sprayed onto the flue gases and the sulfur dioxide reacts with the alkaline slurry and produces a solid waste product called calcium sulfite

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16
Q

What is wet scrubbing

A

When the acidic sulfur dioxide is removed from flue gases by reacting with an alkali

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17
Q

How are Group 2 compounds used in agriculture

A

Calcium hydroxide is used to neutralise acidic soils

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18
Q

How are Group 2 compounds used in pharmaceutical products

A

Magnesium hydroxide is used in some indigestion tablets as an antacid

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19
Q

Explain the trend of the boiling points of the halogens when you go down the group

A

They increase as you go down the group because of the increasing strength of the van der Waals forces as the size and relative mass of the molecules increases

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20
Q

Explain the trend of electronegativity as you go down the group of halogens

A

It decreases as you go down because larger atoms attract electons less than smaller ones because there is more shielding and more distance between the outer electron and the nucleus

21
Q

What type of agent is an halogen

A

Oxidising agents

22
Q

What is the rule when it comes to displacement reactions involving halogens and halide ions

A

The halogen will displace a halide from solution if the halide is below it in the periodic table

23
Q

What happens when KBr reacts with Cl2

A

Orange solution (Br2) is formed

24
Q

What happens when KI (potassium iodide) reacts with Br2

A

Brown solution is formed (I2)

25
Q

What colur is an halide ion in solution

A

They are colourless in solution

26
Q

How is bleach made

A

Mix chlorine gas with cold, dilute sodium hyrdroxide solution at room temperature you get sodium chlorate(I) solution (NaClO(aq)) - This is bleach

27
Q

What happens to chlorine in the reaction when bleach is made

A

It is being oxidised and reduced
This is called disproportionality

28
Q

Give the equation for when you mix chlorine and water and what chlorine is undergoing in this reaction

A

Cl2(g) + H2O(l) ⇌ 2H+(aq) + Cl-(aq) + ClO-(aq)
Disproportionality

29
Q

Why is chlorine useful in water treatment

A

Kills disease-causing microorganism, prevents the growth of algae, eliminates bad tastes and smells and removes discolouration caused by organic compounds

30
Q

What are the risks of using chlorine to treat water

A

Irritates respiratory system if it is breathed in
Liquid chlorine can cause burns on the skin and eyes

31
Q

What happens when a normal halide reacts with concentrated sulfuric acid

A

NaX + H2SO4 -> NaH2SO4 + HX

32
Q

What happens when a strongly reducing halide agent reacts with sulfuric acid

A

2HX + H2SO4 -> X2 + SO2 +2H20

33
Q

What happens when a Iodide halide ion reacts with H2SO4

A

It can reduce the SO2 to H2S or S

34
Q

How do you test for halides

A

The silver nitrate test
Add dilute nitric acid to remove ions which might interfere wtith the test then add a few drops of silver nitrate solution and a precipitate is formed of the silver halide

35
Q

What is the equation for the silver nitrate test

A

Ag+(aq) + X-(aq) -> AgX(aq)
X = Cl, Br or I

36
Q

What are the results for the halide test

A

Chloride ions = white precipitate
Bromide ions = cream precipitate
Iodide ions = yellow precipitate

37
Q

How can you be extra sure with the results from a silver nitrate solution - how can you interpret the results

A

Add ammonia solution because each silver halide has a different solubility in ammonia
Chloride = dissolves in dliute ammonia
Bromide = dissolves in concentrated ammonia
Iodide = insoluble in concentrated ammonia

38
Q

How do you test for Group 2 ions

A

Flame test
Dip nichrome wire loop in concentrated hydrochloric acid to clean and dip inunknown compound
Hold loop in the clear blue part of a Bunsen burner flame and observe colour change

39
Q

How do you interpret the results of the Group 2 flame test

A

Ca2+ = brick red
Sr2+ (Strontium) = red
Ba2+ = pale green

40
Q

How do you test for Group 2 ions without doing a flame test

A

Add NaOH dropwise to a test tube containing the metal solution and observe the precipitate that forms
Keep adding it in excess and record any changes that you see

41
Q

How do you interpret the results of the non-flame test Group 2 ions test (not in excess)

A

Mg2+ = slight white precipitate
Ca2+ = slight white precipitate
Sr2+ = slight white precipitate
Ba2+ = no change

42
Q

How do you interpret the results of the non-flame test Group 2 ions test (in excess)

A

Mg2+ = white precipitate
Ca2+ = slight white precipitate
Sr2+ = slight white precipitate
Ba2+ = no change

43
Q

Is ammonia gas alkaline or acidic

A

Alkaline

44
Q

What is the test for ammonium ions

A

Add some dilute sodium hydroxide solution to substance in test tube and gently heat
If ammonium ions are present it produces ammonia gas and water when it reacts with hydroxide
Use a damp red litmus paper to test for the ammonia gas and if it turns blue then there are ammonium ions in the sample

45
Q

What is the equation for when ammonium ions react with hydroxide

A

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

46
Q

How do you test for hydroxide ions

A

Hyrdroxide ions make solutions alkaline so if you dip a red litmus paper in a soltution that contains hydroxide ions it will turn blue or you can use a different pH indicator

47
Q

What is the test for carbonate ions (1)

A

Add dilute hydrochloric acid to a solution containing carbonate ions it will fizz because the carbonate ions react with hydrogen ions to produce carbon dioxide

48
Q

What is the equation for when carbonate ions react with hydrogen

A

CO3 2- (aq) + 2H+(aq) -> CO2(g) + H2O(l)

49
Q

How can you test for carbonate ions (2)

A

Bubble the solution’s gas into a test tube of limewater and if carbonate ions are present in the solution then it will turn cloudy because CO2 turns limewater cloudy

Chemistry (9 decks)

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