Groups 1 and 2

Question 1

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

Answer 1

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

Question 2

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

Answer 2

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

Question 3

What are the two main problems with a flame test?

Answer 3

• 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

Question 4

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

Answer 4

They become more vigorous

Question 5

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

Answer 5

2M + O2 -> 2MO

Question 6

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

Answer 6

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

Question 7

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

Answer 7

The reactions become more vigorous as you go down the group

Question 8

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

Answer 8

M(s) + Cl₂ (g) -> MCl₂(s)

Question 9

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

Answer 9

Chlorides containing M²⁺ and Cl⁻ ions

Question 10

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

Answer 10

After magnesium, they react with increasing vigour down the group

Question 11

How can you tell a metal is reacting with water?

Answer 11

You can see effervescence

Question 12

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

Answer 12

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

Question 13

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

Answer 13

M(s) + 2H₂O(l) →M(OH)₂(aq) + H₂(g)

Question 14

How does magnesium react when heated in steam?

Answer 14

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

Question 15

Give the equation for the reaction between magnesium and steam

Answer 15

Mg(s) + H₂O(g) → MgO(s) + H₂(g)

Question 16

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

Answer 16

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

Question 17

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

Answer 17

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

Question 18

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

Answer 18

That the solids react to form a colourless solution

MO(s) + H₂0(l) -> M(OH)₂ (aq)

Question 19

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?

Answer 19

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

Question 20

What is limewater a name for?

Answer 20

A saturated aqueous solution of calcium hydroxide

Question 21

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

Answer 21

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

Question 22

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

Answer 22

• 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

Question 23

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

Answer 23

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

Question 24

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

Answer 24

Salt and water making it a neutralisation reaction

Question 25

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

Answer 25

A white solid reacts to form a colourless solution

Question 26

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

Answer 26

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

Question 27

What are the trends in solubility of group 2 sulphates?

Answer 27

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

Question 28

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

Answer 28

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)

Question 29

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?

Answer 29

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

Question 30

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

Answer 30

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

Question 31

What is thermal stability?

Answer 31

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

Question 32

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

Answer 32

- 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

Question 33

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

Answer 33

- 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

Question 34

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

Answer 34

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

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

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

Answer 37

- 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

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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

Question 40

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

Answer 40

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)

Question 41

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

Answer 41

- 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)

Question 42

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

Answer 42

``` Lithium - red Sodium - yellow/orange Potassium - lilac Rubidium - red/purple Caesium - blue/ violet ```

Question 43

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

Answer 43

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