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chemistry🧪🔫 > 8) GROUP 2 > Flashcards

8) GROUP 2 Flashcards

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1
Q

what are the physical properties of group 2 elements?

A

-metal
-reactive metals
-not occur in their natural form
-found in stable compounds

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2
Q

what is the most common type of reactions in group 2 elements?

A

redox

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3
Q

give an example of a group 2 element acting as a reducing agent?

A

-Ca –> Ca2+ + 2e-
-Ca is oxidised
-reduced another species

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4
Q

what is formed when group 2 elements react with O2?

A

-metal oxide
-general formula=MO

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5
Q

what can you observe when magnesium burns with oxygen?

A

-white light
-forms MgO

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6
Q

what is formed when group 2 elements react with water?

A

-alkaline hydroxide
-hydrogen gas

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7
Q

what is the general formula of alkaline hydroxides?

A

M(OH)2

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8
Q

what are the reactivity trends in group 2?

A

-increases down the group

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9
Q

what are the products of group 2 elements reacting with dilute acids?

A

-salt
-hydrogen gas

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10
Q

why does the reactivity increase down the group?

A

-attraction between nucleus + electron decreases
-increasing atomic radius + shielding
-ionisation energy decrease

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11
Q

what are the products of group 2 oxides reacting with water?

A

-release hydroxide ions
-form metal hydroxide

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12
Q

what is the solubility of group 2 hydroxides in water?

A

increases down the group

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13
Q

what happens when the solution of group 2 oxides become more saturated?

A

form a solid precipitate

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14
Q

what are the uses of group 2 compounds as bases?

A

-agriculture
-medicine

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15
Q

how are group 2 bases used in agriculture?

A

-calcium hydroxide added to fields= increase pH
-neutralises acid in soil= form neutral water

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16
Q

what are the uses of group 2 bases in medicine?

A

-antacids= treat indigestion
-magnesium/calcium carbonates
-neutralisation reactions

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17
Q

what are some properties of halogens?

A

-most reactive
-non-metal
-do not occur in natural state
-occur as halide ions

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18
Q

at room temp + pressure how do the halogens exist?

A

diatomic mol.

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19
Q

what is the structure of halogens in their solid state?

A

form lattices with simple molecular structure

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20
Q

what is the trend in boiling point down the halogen group?

A

-boiling increases
-more energy required to break
intermolecular forces

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21
Q

what happens during a halogen redox reaction?

A

-each halogen atom reduced
-gain 1e-
-form 1- halide ionw

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22
Q

why is the halogen an oxidising agent in a redox reaction?

A

species loses its e- to halogen=oxidised

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23
Q

what do the results of the displacement reactions show?

A

reactivity decreases down the group

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24
Q

describe the procedure of halogen-halide displacement reactions

A

-halogen solution is added to the aq solution other halides
-if halogen added is more reactive than halide:
– halogen displaces halide
–solution changes colour

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25
Q

what colour is iodine + bromine in water?

A

orange-brown

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26
Q

how can we tell the difference between iodine + bromine in water?

A

-organic non-polar solvent can be added (cyclohexane)
-non polar halogens dissolve more readily (than cyclohexane)

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27
Q

what colour is iodine in a cyclohexane solution?

A

violet

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28
Q

state the full equation of chlorine and bromide

A

Cl2 (aq) + 2NaBr (aq) –> 2NaCl (aq) + Br2 (aq)

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29
Q

during the reaction of chlorine with bromine what is reduced and what is oxidised?

A

-reduced= chlorine
-oxidised= bromine

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30
Q

describe the trends in reactivity in halogens

A

-atomic radius increases
-shielding increases
-less nuclear attraction down the group
-reactivity decreases

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31
Q

what is disproportionation?

A

-redox reaction
-same element is both oxidised + reduced

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32
Q

what are 2 examples of disproportionation reactions?

A

-reaction of chlorine with water
-reaction of chlorine with cold dilute aq sodium hydroxide

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33
Q

what happens during the disproportionation reaction of chlorine + water

A

-chlorine gets both oxidised + reduced
-for each chlorine atom one gets oxidised and the other atom gets reduced

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34
Q

state the equation of the reaction of chlorine with cold, dilute aq sodium hydroxide

A

Cl2 (aq) + 2NaOH –> NaCl (aq) + NaClO (aq) + H2O (l)

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35
Q

what happens during the disproportionation of chlorine with cold, dilute sodium hydroxide?

A

-chlorine gets both oxidised + reduced
-oxidised= increase in oxidation number
-reduced= decrease in oxidation number

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36
Q

what are 2 ways in which chlorine is used to treat water?

A

-safe to drink
-kill bacteria

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37
Q

how does adding chlorine to water make it safe to drink?

A

-reacts to form sterilising agent HClO
-HClO dissociates in water = ClO-

38
Q

why is using chlorine beneficial in treating water?

A

-outweigh the risks of toxic effects
-possible risks of the formation of chlorinated hydrocarbons

39
Q

what is the test for halide ions?

A

precipitation reactions with aq silver ions

40
Q

what happens during the precipitation reactions with aq silver ions?

A

-aq halide ions react with aq silver ions
-form precipitates= silver halides

41
Q

what is the general formula of the precipitation with aq silver ions?

A

Ag+ (aq) + X- (aq) –> AgX (s)

42
Q

when carbonates react with acids what do they form?

A

CO2

43
Q

describe the procedure of the test for carbonates

A

-small amount of dilute HCl added to test tube
-equal amount of sodium carbonate added to test tube
-bung with delivery tube attached to test tube
-delivery tube= deliver gas into different test tube= containing lime water
-CO2 react to form white precipitate= lime water cloudy

44
Q

describe the procedure of testing for sulfates

A

-acidify sample with dilute HCl
-add few drops of aq barium chloride (barium nitrate can be used too)
-sulfate present= white precipitate formed

45
Q

what shows a positive result in the test for sulfates?

A

white precipitate

46
Q

describe the test for ammonium ions

A

-react with warm aq NaOH = form ammonia gas
-unlikely to see bubbles= soluble in water
-ammonia identified by turning red litmus paper blue

47
Q

how can ammonia gas be identified?

A

turning red litmus paper into blue

48
Q

how can halide ion sbe identified in an unknown solution?

A

-dissolving solution in nitric acid
-add silver nitrate solution (drops)

49
Q

why is nitric acid used in testing for halide ions?

A

prevent any false positive results from carbonate ions precipitating with silver ions

50
Q

what happens when silver nitrate solution is added to an unknown halide solution dissolved in nitric acid?

A

precipitate of silver halide is formed

51
Q

what colour is silver chloride?

A

white precipitate

52
Q

what colour is silver bromide?

A

cream precipitate

53
Q

what colour is silver iodide?

A

yellow precipitate

54
Q

why is ammonia used as a follow up experiment after testing for halide ions?

A

-white, cream + yellow look similar
-determine which halide is present

55
Q

what halide is present if the precipitate dissolves in DILUTE ammonia?

A

chloride

56
Q

what halide is present if it ONLY dissolves in conc. ammonia

A

bromide

57
Q

what halide is present if it does not dissolve in dilute or conc. ammonia?

A

iodide

58
Q

what is the correct sequence of test for anions?

A

1) carbonate
2) sulfate
3) halides

59
Q

why does the carbonate test go first when testing annions?

A

-neither sulfate or halide produce bubbles
-carried out without the possibility of an incorrect conclusion
-no bubbles=no carbonate present

60
Q

why does the sulfate test go second when testing anions?

A

-barium carbonate= white + insoluble
-sulfate test on carbonate= white precipitate too
-have to do carbonate test first = no carbonate present

61
Q

why is the halide test last when testing anions?

A

-silver carbonate + silver sulfate= insoluble in water + form precipitate
-rule out the possibilities of being a carbonate or sulfate

62
Q

what changes in the procedure during the carbonate test of a mixture of ions?

A

-see bubbles= continue adding nitric acid= until bubbling stops
-all carbonate removed= none left to react in next test

63
Q

what changes occur in the procedure of the sulfate test of a mixture of ions?

A

-solution left from carbonate= add excess Ba(NO3)2
-sulfate ions=precipitate=barium sulfate
-filter solution=remove barium sulfate

64
Q

what is something you need to remember when carrying out the sulfate test on a mixture of ions?

A

-if intend to test halide ions:
-not use BaCl2= chlorine could show up in halide test

65
Q

what changes happen to the procedure when testing for halide ions in a mixture of ions?

A

-solution left from sulfate test= add AgNO3
-all carbonate + sulfate removed= any precipitate= involves halides
-add NH3= confirm halide

66
Q

what is formed when aq ammonium ions + aq hydroxide ion react?

A

ammonia gas

67
Q

describe the procedure of the test for ammonium ion (CATION)

A

1) aq NaOH added to solution of ammonium ion
2) ammonia gas produced (unlikely to see bubbles= soluble in water)
3) mixture warmed + ammonia gas released
4) ammonia turn pH indicator paper blue (alkali)

68
Q

(LEQ) Explain why barium is more reactive than calcium?
[4]

A

-atomic radius increases
-more shielding
-nuclear attraction decreases
-easier to remove e-

69
Q

(LEQ)
Old samples of magnesium oxide become contaminated with magnesium carbonate.

-Suggest how this contamination takes place.
[1]

A

MgO has reacted with CO2

70
Q

(LEQ)
A student added an excess of hydrochloric acid to an old sample of magnesium oxide that is contaminated with magnesium carbonate.

State two observations that the student would make
[2]

A

-Solid dissolves
-Fizzing

71
Q

LEQ
A student added an excess of hydrochloric acid to an old sample of magnesium oxide that is contaminated with magnesium carbonate

-Explain, with the aid of equations, why the resulting solution contained only one dissolved compound of magnesium.
[3]

A

-MgO + 2HCl –> MgCl2 + H2O
-MgCO3 + 2HCl –>MgCl2 + CO2 + H2
-both reactions form magnesium chloride

72
Q

LEQ
Magnesium reacts with oxygen to form magnesium oxide.

2Mg(s) + O2(g) –> 2MgO(s)

  • Use oxidation numbers to show that oxygen has been reduced in its reaction with magnesium.
A

-Oxidation state goes from 0 in O2
–> -2 in MgO

73
Q

LEQ
This question is about elements and compounds of Group 2 of the Periodic Table.

When calcium is added to water, a vigorous reaction takes place, releasing hydrogen gas.

Ca(s) + 2H2O(I) –>Ca{OH)2(aq) + H2(g)

Suggest a value for the pH of the solution formed in this reaction.

A

9~14

74
Q

LEQ
In their reactions, calcium and strontium each lose electrons to form ions with a 2+ charge. The first and second ionisation energies of calcium and strontium are shown below.
Ca =1st IE =590
2nd IE = 1145
Sr= 1st IE= 550
2nd IE= 1064
Write an equation, with state symbols, to represent the second ionisation energy of calcium

A

Ca+(g) –> Ca2+(g) + e−

75
Q

LEQ
In their reactions, calcium and strontium each lose electrons to form ions with a 2+ charge. The first and second ionisation energies of calcium and strontium are shown below.
Ca =1st IE =590
2nd IE = 1145
Sr= 1st IE= 550
2nd IE= 1064
Why are the second ionisation energies of calcium and strontium greater than their first ionisation energies

A

-same number of protons or same nuclear charge attracting
-less electrons/
-electron removed from an ion/
-less electron-electron repulsion (not less shielding)/
-ion is smaller

76
Q

LEQ
In their reactions, calcium and strontium each lose electrons to form ions with a 2+ charge. The first and second ionisation energies of calcium and strontium are shown below.
Ca =1st IE =590
2nd IE = 1145
Sr= 1st IE= 550
2nd IE= 1064
Explain why the first and second ionisation energies of strontium are less than those of calcium

A

-atomic radii of Sr > atomic radii of Ca/
-Sr has electrons in shell further from nucleus than Ca/
-Sr has electrons in a higher energy level/
-Sr has more shells
-Therefore less attraction
-Sr has more shielding than Ca

77
Q

Carbon dioxide can be prepared easily in the laboratory by the action of heat on most carbonates. Construct an equation to illustrate this reaction.

A

CaCO3 –> CaO + CO2

78
Q

LEQ
A student prepared an aqueous solution of calcium chloride by reacting calcium with hydrochloric acid. Calcium chloride contains Ca2+ and Cl– ions.

(a) Complete and balance the following equation for this reaction.

……Ca(s) + …… HCl(aq) –> ……. CaCl2(aq) + …………

A

Ca(s) + 2 HCl(aq) –>CaCl2(aq) + H2(g)

79
Q

LEQ
A student prepared an aqueous solution of calcium chloride by reacting calcium with hydrochloric acid. Calcium chloride contains Ca2+ and Cl– ions.
This is a redox reaction. Use oxidation states to show that calcium has been oxidised

A

-In Ca, oxidation state = 0 and
-In CaCl2, oxidation state = +2
- Oxidation number increases from Ca to CaCl2

80
Q

LEQ
The reaction of strontium with water is a redox reaction. A student reacted 0.438 g of strontium with 200 cm3 of water.

Sr(s) + 2H2O(l) –> Sr(OH)2(aq) + H2(g)

Use oxidation numbers to show that strontium has been oxidised in this reaction.

A

In Sr, oxidation number = 0

In Sr(OH)2, oxidation number = (+)2

81
Q

LEQ
The reaction of strontium with water is a redox reaction. A student reacted 0.438 g of strontium with 200 cm3 of water.

Sr(s) + 2H2O(l) –> Sr(OH)2(aq) + H2(g)

Calculate how many moles of Sr were reacted.

Ar: Sr, 87.6

A

0.438/87.6 = 5.00x10^−3 / 0.00500 mol

82
Q

LEQ
The reaction of strontium with water is a redox reaction. A student reacted 0.438 g of strontium with 200 cm3 of water.

Sr(s) + 2H2O(l) –> Sr(OH)2(aq) + H2(g)

Calculate the volume, in dm3, of H2(g) produced. You can assume that, under the experimental conditions, 1.00 mol of H2(g) has a volume of 24.0 dm3.

A

0.00500 x 24.0 = 0.120 dm3

83
Q

LEQ
Calculate the volume, in dm3, of H2(g) produced. You can assume that, under the experimental conditions, 1.00 mol of H2(g) has a volume of 24.0 dm3.

Calculate the concentration, in mol dm–3, of the Sr(OH)2 produced.

A

0.00500 x 1000/200 = 0.0250 mol/dm−3

84
Q

LEQ
Chewing chalk has been used for many years to combat excess stomach acid and indigestion tablets often contain calcium carbonate, CaCO3. Suggest, with the aid of an equation, how these tablets work.

A

-CaCO3 reacts with HCl
-CaCO3 + 2HCl–> CaCl2 + H2O + CO2

85
Q

LEQ
Magnesium reacts with carbon dioxide forming a mixture of magnesium oxide, MgO, and carbon.

Write an equation, with state symbols, for this reaction

A
86
Q

LEQ
What is the formula of calcium chloride?

A

2Mg (s) + CO2 (g) –> 2MgO (s) + C (s)

87
Q

LEQ
State the trend in reactivity of the Group 2 elements with oxygen. Explain your answer.

A

-reactivity increases (down the group)
-atomic radius increases
-more shielding
-The nuclear attraction decreases
-easier to remove (outer) electrons

88
Q

LEQ
Magnesium oxide has an extremely high melting point which makes it suitable as a lining for furnaces.

Explain, in terms of its structure and bonding, why magnesium oxide has this property.

A

-giant structure
-ionic
-strong forces

89
Q

LEQ
What is the trend in the ease of thermal decomposition of Group 2 carbonates?

A

-decreases down the group

90
Q

LEQ
Calcium carbonate thermally decomposes into calcium oxide and carbon dioxide as shown in the equation.

CaCO3 (s) → 2CaO(s) + CO2(g)

Magnesium carbonate also thermally decomposes. Describe the difference in the ease of thermal decomposition between magnesium carbonate and calcium carbonate. Use ideas about charge density and polarisation in your answer.

A

-MgCO3 decomposition easier than CaCO3
-Mg2+ higher charge density than Ca2+
-both have the same
charge but Mg2+ has a smaller ionic radius
-So Mg2+ will polarise CO32- more than Ca2+ can

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