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A-Level Chemistry > Topic 4A: Group 1 and 2 > Flashcards

Topic 4A: Group 1 and 2 Flashcards

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1
Q

Define the first ionisation energy of an element

A

the energy needed to remove an electron from each atom in one mole of atoms in the gaseous state

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2
Q

Define the second ionisation of an element

A

the energy required to remove an electron from each singly charged postive ion in one mole of positive ions in the gaseous state

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3
Q

What is the general equation for first ionisation energy, using M?

A

M(g) —> M+(g) + e-

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4
Q

What is the general equation for second ionisation energy, using M?

A

M+(g) —> M2+(g) + e-

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5
Q

What is the trend of ionisation energies in Group 2?

A

decrease, as a result an increase in reactivity down the group

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6
Q

Name the factors to consider when explaining trends in ionisation energies

A
  • the nuclear charge, or number of protons
  • the obital in which the electron exists
  • the shiedling effect
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7
Q

Give reasons why ionisation energy decreases down Group 2

A
  • increased nuclear charge=force of attraction for the electron being removed increases
  • as each quantum shell is added, energy of the outermost electron increases
  • as the number of filled inner shells increases, their force of repulsion on the electron being removed increases, so a decrease in ionisation energy
  • the effect of the last 2 factors outweighs the higher nuclear charge so ionisation energy decreases
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8
Q

What is the general equation for Group 2 metals and oxygen?

A

2M (s) + O2(g) —> 2MO (s)

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9
Q

What is the general equation for Group 2 metals and chlorine?

A

M(s) + Cl2(g) —> MCl2(s)

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10
Q

What observations would be made when Group 2 metals react with oxygen?

A
  • very bright flame
  • formation of a white solid
  • barium = most reactive
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11
Q

What is the general equation for Group 2 metals and water?

A

M(s) + 2H2O(l) —> M(OH)2(aq) + H2(g)

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12
Q

What happens when calcium reacts with water?

A

Calcium hydroxide produced is only slightly soluble in water so is a solid not aqueous- the liquid in the experiment goes cloudy as a precipitate of calcium hydroxide forms

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13
Q

Give the equation for magnesium heated with steam

A

Mg(s) + H2O(g) —> MgO(s) + H2(g)

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14
Q

What are basic oxides?

A

oxides of metals that react with water to form metal hydroxides, and with acids to form salts and water

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15
Q

What’s the test for carbon dioxide?

A

limewater goes cloudy as a white precipatate froms

equation: CO2 + Ca(OH)2 —> CaCO3 + H2O

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16
Q

What is the trend in solubility for Group 2 hydroxides?

A

increases down the group

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17
Q

How do you neutralise hydrochloric acid in the stomach?

A

milk of magnesia (magnesium hydroxide solution)

equation: Mg(OH)2 + 2HCl –> MgCl2 + 2H2O

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18
Q

What is the products of Group 2 oxides and hydroxides with acids?

A

salt and water (neutralosation)

observation: white solid reacts to form colourless solution

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19
Q

What is the trend in solubility of Group 2 sulfates?

A

decreases down the group
magnesium sulfate is soluble
calcium sulfate is slightly soluble
strontium sulfate and barium are insoluble

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20
Q

How do you test for sulfate ions?

A

adding a solution containing barium ions to from a white barium sulfate precipitate e.g. dilute nitric/HCl acid and barium nitrate solution (H+ ions are present to prevent barium carbonate forming as a white precipitate)

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21
Q

Define thermal stability

A

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

22
Q

Why is the thermal stability different for Group 1 and 2 nitrates and carbonates?

A
  1. the charge on a Group 2 cation is double Group 1
  2. the size and ionic radius of a Group 2 cation is smaller than a Group 1 cation
  3. the nitrate and carbonate ions are more complex than the Cl-
23
Q

What happens when a Group 2 nitrate decomposes?

A

forms metal oxide, nitrogen dioxide gas and oxygen

24
Q

What happens when a Group 2 carbonate decomposes?

A

the larger, complex ion changes into a smaller, more stable oxide ion (O2-) by decomposing and releasing carbon dioxide. forms metal oxide and carbon dioxide

25
Q

State the general equation for metal nitrates with a lesser decomposition

A

metal nitrate —> metal nitrite + oxygen

2MNO3(s) —> 2MNO2(s) + O2(g)

26
Q

State the general equation for metal nitrates with a greater decomposition

A

metal nitrate —> metal oxide + nitrogen dioxide + oxygen

27
Q

How can you tell lesser decomposition occurs?

A

no brown fumes observed

28
Q

How can you tell greater decomposition occurs?

A

brown fumes observed

29
Q

Which Group 1 nitrate decomposes to produce brown fumes?

A

lithium nitrate

30
Q

When does greater decomposition occur of metal nitrates?

A
  • the cation has a 2+ charge, all of Group 2

- the cation has a 1+ charge and is also the smallest Group 1 cation, lithium

31
Q

What observations are made for the decomposition of carbonates?

A

no observations made because metal carbonates and metal oxides are white and CO2 is colourless

32
Q

Give the equation of the only Group 1 carbonate that decomposes

A

lithium carbonate

Li2CO3 —> Li2O + CO2

33
Q

When does decomposition occur of metal carbonates?

A
  • the cation has a 2+ charge, all of Group 2

- the cation has a 1+ charge and is also the smallest Group 1 cation, lithium carbonate

34
Q

How do you carry out a flame test?

A
  1. wear safety goggles and a lab coat. within a fume cupboard, light a Bunsen burner
  2. using a dropper add a few drops of concentrated HCL to the solid so it starts to dissolve (coverts it to a chloride which are most volatile)
  3. dip a clean nichrome or platinum inoculating loop into the mixture to obtain a sample
  4. hold the end of the wire in the flame and observe the colour
35
Q

What is formed when group 1 nitrates decompose?

A

forms group 1 nitrite and oxygen

e.g. 2MNO3 –> 2MNO2 + O2

36
Q

What is the flame test colour of the lithium ion?

A

red

37
Q

What is the flame test colour of the sodium ion?

A

yellow/orange

38
Q

What is the flame test colour of the potassium ion?

A

lilac

39
Q

What is the flame test colour of the rubidium ion?

A

red/purple

40
Q

What is the flame test colour of the caesium ion?

A

blue/violet

41
Q

What is the flame test colour of the beryllium ion?

A

no colour

42
Q

What is the flame test colour of the magnesium ion?

A

no colour

43
Q

What is the flame test colour of the calcium ion?

A

brick-red

44
Q

What is the flame test colour of the strontium ion?

A

crimson-red

45
Q

What is the flame test colour of the barium ion?

A

apple green

46
Q

Give details about the reaction between magnesium and water

A

reacts very slowly
doesn’t proceed completely
magnesium will be covered in bubbles of hydrogen gas
not a vigorous reaction

47
Q

What is the trend in pH value of Group 2 hydroxides?

A

increases because the solubility increases so alkalinity increases down the group

48
Q

How do you test for ammonium ions?

A 
-add sodium hydroxide solution and warm:
NH4+ + OH- ---> NH3 + H2O
or NH4Cl + NaOH ---> NH3 + H2O + NaCl
-ammonia gas is produced which can be identified by turning damp red litmus paper blue or when hydrogen chloride gas reacts with ammonia it forms white fumes of ammonium chloride:
NH3 + HCl --> NH4Cl
49
Q

What causes the colours in a flame test?

A
  • electron transitions
  • electrons absorb energy from the flame and move to higher energy levels ( from ground state to excited state)
  • when electrons fall back down to lower energy levels , they release energy
  • if this energy corresponds to radiation in the visible light spectrum then a colour is observed
50
Q

Which group 2 element doesn’t react with water?

A

beryllium

A-Level Chemistry (20 decks)

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