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A Level Chemistry > Groups 1 and 2 > Flashcards

Groups 1 and 2 Flashcards

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1
Q

In a flame test, why do you add HCL to the metal compound you are going to test?

A

To dissolve the solid and HCL will convert any metal compound to a chloride as chlorides are more volatile than other salts so are more likely to give better results

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2
Q

In a flame test, what do you use to obtain the sample of the compound?

A

A metal wire made of platinum or nichrome , or you can use a silica rod

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3
Q

What are the two main problems with a flame test?

A
  • Many compounds contain small amounts of sodium compounds as impurities so the intense colour of sodium can mask other colours
  • describing colours with words is subjective as people have different levels of colour vision and a word description of a colour may mean different colours to different people
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4
Q

What is the trend of the reaction of group 2 metals and oxygen as you go down the group?

A

They become more vigorous

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5
Q

What is the general equation for group 2 metals reacting with oxygen?

A

2M + O2 -> 2MO

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6
Q

How do you usually store barium to protect it from the air as its most reactive with oxygen?

A

Under oil to keep it from reacting with oxygen and water vapour in the air

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7
Q

What is the trend in the reaction of group two metals and chlorine as you go down the group?

A

The reactions become more vigorous as you go down the group

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8
Q

What is the general equation for the reaction of group 2 metals and chlorine gas?

A

M(s) + Cl₂ (g) -> MCl₂(s)

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9
Q

What are the products of a reaction between a metal and chlorine?

A

Chlorides containing M²⁺ and Cl⁻ ions

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10
Q

What is the trend in group 2 metals and the reaction with water as you go down the group?

A

After magnesium, they react with increasing vigour down the group

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11
Q

How can you tell a metal is reacting with water?

A

You can see effervescence

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12
Q

What can you see when you react calcium with water and why

A

You can see effervescence and then the liquid goes cloudy as a precipitate of calcium hydroxide forms as calcium hydroxide is only slightly soluble in water

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13
Q

What is the general equation for the reaction of group 2 metals with water?

A

M(s) + 2H₂O(l) →M(OH)₂(aq) + H₂(g)

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14
Q

How does magnesium react when heated in steam?

A

It rapidly forms magnesium oxide (a white solid) and hydrogen gas in a vigorous reaction

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15
Q

Give the equation for the reaction between magnesium and steam

A

Mg(s) + H₂O(g) → MgO(s) + H₂(g)

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16
Q

In the experiment of reacting magnesium and steam, what happens to the hydrogen formed and why?

A

The hydrogen formed is burned as it leaves the tube to prevent the escape of a highly flammable gas into the laboratory

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17
Q

What kind of oxides are group 2 oxides classed as and what does this mean in terms of reaction?

A

They are classed as basic oxides which means they can react with water to form alkalis

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18
Q

What observation can be made from the reaction of group 2 oxides with water? What is the general equation?

A

That the solids react to form a colourless solution

MO(s) + H₂0(l) -> M(OH)₂ (aq)

19
Q

Whats the trend in solubility of group 2 hydroxides and so what does that mean for the trend of the maximum alkalinity of the solutions formed going down the group?

A

Group 2 hydroxides increase down the group so the maximum alkalinity of the solutions formed also increases down the group

20
Q

What is limewater a name for?

A

A saturated aqueous solution of calcium hydroxide

21
Q

How can you test for carbon dioxide and give the equation for the reaction that takes place

A

By bubbling the carbon dioxide through calcium hydroxide to produce calcium carbonate which can be seen as a white precipitate as its insoluble in water

CO2 + Ca(OH)2 -> CaCO3 + H2O

22
Q

What is milk of magnesia, what does it do, how does it work, what’s the equation for the reaction that takes place?

A
  • milk of magnesia is a suspension of magnesium hydroxide
  • it acts as an antacid and so works as an indigestion remedy
  • it works by neutralising some of the hydrochloric acid in the stomach to settle the symptoms of indigestion
  • Mg(OH)2 + 2HCl -> MgCl2 + 2H20
23
Q

How does milk of magnesia not pose a threat to health?

A

As magnesium hydroxide has been low solubility meaning the concentration of OH- ions in the medicine is also very low and so does not pose a risk to human health

24
Q

What do group 2 oxides and hydroxides form when they react with acids? What does this make the reaction?

A

Salt and water making it a neutralisation reaction

25
Q

What observations can be made from the reactions of group 2 hydroxides and oxides with acids?

A

A white solid reacts to form a colourless solution

26
Q

Why do farmers use lime to control soil acidity so a greater yield of crops can be obtained? Give an equation for the reaction that happens if the acid in the soil is nitric acid

A

As lime is mostly calcium hydroxide which neutralises excess acidity in the soil:
Ca(OH)2 + 2HNO3 -> Ca(NO3)2 + 2H2O

27
Q

What are the trends in solubility of group 2 sulphates?

A

As you go down the group, solubility of the sulphates decreases

28
Q

How can you test for the presence of sulphate ions in an aqueous solution and give the ionic equation to show this

A

By adding a solution containing barium ions (usually barium chloride or barium nitrate)as any sulfate ions in the solution will react will react with the added barium ions to form a white precipitate of barium sulphate as barium sulphate is insoluble:
Ba2+(aq) + so₄²⁻(aq) -> BaSO₄(s)

29
Q

When testing for sulphate ions in an aqueous solution by adding a solution containing barium ions, why is dilute nitric or hydrochloric acid added as part of the test?

A

As there are other anions that could also form a white precipitate with barium ions, especially carbonate ions, so the H+ ions from the acid can prevent the barium carbonate from forming as a white precipitate

30
Q

Give a use of barium sulphate. How is it that it’s not poisonous for this use?

A

In hospitals it’s given as a barium ‘meal’ which is taken by the patient before an x-ray so that soft tissue will show up more clearly due to the dense solid formed by the barium sulphate. It’s not poisonous because it is insoluble as the barium ions are not free to move

31
Q

What is thermal stability?

A

A measure to the extent to which a compound decomposes when heated

32
Q

Give three reasons why the thermal stability of group 2 nitrates and carbonates is very different compared with a group 1 chloride like sodium chloride

A
  • the charge on a group 2 cation is double that of a group 1 cation
  • the size of a group 2 cation is smaller than that of the group 1 cation in the same period
  • the nitrate (NO3-) and carbonate (CO32-) anions are more complex than the Cl- ion
33
Q

What 3 factors explain why when group 2 nitrates and carbonates are heated, they decompose instead of melt?

A
  • the larger, more complex nitrate ion can change into the smaller, more stable nitrite ion by decomposing and releasing oxygen and/or nitrogen dioxide gas
  • the larger, more complex carbonate ion can change into the smaller, more stable oxide ion by decomposing and releasing carbon dioxide gas
  • the stabilities of the nitrate ion and carbonate anions are influenced by the charge and size of the cations present so smaller and more highly charged cations affect the nitrate and carbonate anions more
34
Q

When heating group 1 and 2 nitrates, what visible changes can be observed?

A

Group 1 and 2 nitrates start off as white solids and can decompose to give brown fumes and if the nitrate contains water of crystallisation then steam will also be observed

35
Q

What does it indicate of you heat group 1 and 2 nitrites and no brown fumes are observed? Give the word equation that represents this

A

Then it indicates a lesser decomposition that can be represented by the word equation:
Metal nitrate -> metal nitrite + oxygen

36
Q

What does it indicate of you heat group 1 and 2 nitrites and brown fumes are observed? Give the word equation that represents this

A

It indicates a greater decomposition which can be represented by the word equation:
Metal nitrate -> metal oxide + nitrogen dioxide + water

37
Q

When heating group 1 and 2 nitrates,when does the greater decomposition occur?

A
  • when the the action has a 2+ charge (all of the group 2 nitrates
  • when the cation has a 1+ charge and is also the smallest group 1 cation
38
Q

When you heat carbonates of group one and two elements, what are the changes that are observed?

A

There are no changes observed because the gas given off is colourless and both the carbonate and oxide are white solids

39
Q

When you heat carbonates of group one and two elements, what are the reactions that could happen?

A

They could either decompose to oxides and give off carbon dioxide, or not decompose

40
Q

When group one and group 2 carbonates are heated, which ones decompose.

A

Only lithium carbonate decomposes in group 1 and all of group 2 decompose however with increasing difficulty down the group (similar to the pattern with nitrates)

41
Q

When you heat carbonates of group one and two elements, when does decomposition occur?

A
  • When the cation has a 2+ charge (so all of group two carbonates)
  • when the cation has a 1+ charge and is also the smallest group 1 cation (which is only lithium carbonate)
42
Q

In the flame tests, what colour is each group 1 element from lithium to caesium ?

A 
Lithium - red
Sodium - yellow/orange 
Potassium - lilac
Rubidium - red/purple
Caesium - blue/ violet
43
Q

In the flame tests, what colour is each group 2 element, going from beryllium to barium?

A 
Beryllium- no colour 
Magnesium-  no colour
Calcium- brick red
Strontium- crimson red 
Barium- apple green

A Level Chemistry (4 decks)

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