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(OCR A) A-level Chemistry > Chapter 8 - Reactivity Trends > Flashcards

Chapter 8 - Reactivity Trends Flashcards

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1
Q

What are group 2 metals called?

A

Alkaline earth metals

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2
Q

What type of agent are group 2 metals known as?

A

Reducing agents

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3
Q

How do group 2 metals work as reducing agents?

A

Each metal atom is oxidised, losing two electrons to form 2+ ions which causes another species to gain these electrons and so get reduced

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4
Q

What is formed when a group 2 metal reacts with oxygen?

A

Metal oxide

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5
Q

What is formed when a group 2 metal reacts with water?

A

Metal hydroxide + hydrogen gas

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6
Q

What is formed when a group 2 metal reacts with dilute acids?

A

Salt + hydrogen gas

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7
Q

Why does reactivity increase down group 2 metals?

A
  • Atomic radius increases
  • More inner shells so heleiding increases
  • Nuclear attraction decreases so less energy to lose electrons
  • Formation of 2+ ions requires input of two ionisation energies
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8
Q

Ionisation energies ________ down group 2 elements

A

Decreases

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9
Q

Group 2 elements become _________ reducing agents down the group

A

Stronger

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10
Q

What happens when a group 2 oxide reacts with water?

A

Hydroxide ions released to form alkaline solutions of the metal hydroxide

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11
Q

What is the equation for reaction between calcium oxide and water?

A

CaO(s) + H2O(l) -> Ca2+ (aq) + 2OH- (aq)

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12
Q

What is formed when a solution of calcium oxide reacting with water becomes saturated?

A

Calcium hydroxide precipitate
Ca(OH)2

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13
Q

Solubility of group 2 hydroxides _________ down the group so resulting solutions contain _________ OH- ions and are more _________. Which means pH _________

A

Increases
More
Alkaline
Increases

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14
Q

Compare the solubilities of Mg(OH)2 and Ba(OH)2

A

Mg(OH)2 very slightly souble in water -> low OH- concentration in solution so pH ~ 10
Ba(OH)2 much more soluble in water -> greater OH- concentration in solution so pH ~ 13

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15
Q

What are the uses of calcium hydroxide, Ca(OH)2? Give equation

A

Agriculture - added to fields to increase pH of acidic soils by neutralising the acids in soil
Ca(OH)2 (s) + 2H+ (aq) -> Ca2+ (aq) + 2H2O (l)

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16
Q

What are the uses of magnesium hydroxide Mg(OH)2? Give equation

A

Medicine - treatment for acid indigestion by neutralisation
Mg(OH)2 (s) + 2HCl (aq) -> MgCl2 (aq) + 2H2O (l)

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17
Q

What are the uses of calcium carbonates, CaCO3? Give equation

A

Medicine - treatment for acid indigestion by neutralisation
CaCO3 (s) + 2HCl (aq) -> CaCl2 (aq) + 2H2O (l) + CO2 (g)

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18
Q

Trend in boiling point of halogens down the group?

A

Increases

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19
Q

Why does boiling point increase down group 7 halogens?

A
  • More electrons
  • Stronger London forces
  • More energy required to break intermolecular forces
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20
Q

What type of agent are group 7 halogens known as?

A

Oxidising agents

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21
Q

How do group 7 halogens work as oxidising agents?

A

Each halogen atom is reduced, gaining one electron to form 1- ions which causes another species to lose this electron and so get oxidised

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22
Q

What happens in a displacement reaction of halogens?

A

More reactive halogen displaces halide from solution

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23
Q

Colours of Cl2, Br2 and I2 solution in water?

A

Pale green
Orange
Brown

24
Q

Colours of Cl2, Br2 and I2 solution in cyclohexane?

A

Pale green
Orange
Violet

25
Q

What can displace I-?

A

Chlorine and bromine

26
Q

What can displace Br-?

A

Chlorine

27
Q

What can displace Cl-?

A

Nothing

28
Q

More reactive halogen gets __________ (________ electrons)

A

Reduced
Gains

29
Q

Explain why reactivity decreases down the group 7 halogens?

A
  • Atomic radius increases
  • More inner shells so heleiding increases
  • Nuclear attraction decreases so harder to gain electron
30
Q

Halogens become _______ oxidising agents down the group

A

Weaker

31
Q

What is disproportionation?

A

Redox reaction in which the SAME element is both reduced and oxidised

32
Q

Give the equation for chlorine purifying water?

A

Cl2 + H2O -> HClO + HCl

33
Q

Why is chlorine reacting with cold, dilute aqueous sodium hydroxide a better bleach than reacting chlorine with water?

A

Chlorine has a low solubility in water, so reacting with NaOH allows for a larger concentration of chlorate ions which act as a bleach

34
Q

Give the equation for the reaction between chlorine with cold, dilute aqueous sodium hydroxide?

A

Cl2 + 2NaOH -> NaClO + NaCl + H2O

35
Q

Which ion acts as a bleach?

A

Chlorate (I) ions, ClO-

36
Q

What are the benefits and risks of using chlorine in water treatment?

A

Benefits - kills bacteria
Risks - hazards of toxic chlorine gas and formation of chlorinated compounds

37
Q

How is the carbonate test is carried out?

A

Add dilute HNO3 to solution being tested

38
Q

What is the positive result for a carbonate test?

A

Effervescence (bubbles) to indicate the release of a gas (CO2)

39
Q

How can the gas of a positive carbonate test be tested?

A

Bubble through limewater, it will turn cloudy in the presence of CO2

40
Q

Barium sulfate is ___________ in water

A

Insoluble

41
Q

How is sulfate test carried out?

A

Add Ba(NO3)2 to solution being tested

42
Q

What is a positive result for a sulfate test?

A

White precipitate

43
Q

How is halide test carried out?

A

Add AgNO3 (aq) to aqueous solution of sample being tested

44
Q

What is the positive result of a halide test if CHLORINE is present?

A

White precipitate which is soluble in dilute NH3 (aq)

45
Q

What is the positive result of a halide test if BROMINE is present?

A

Cream precipitate which is soluble in concentrated NH3 (aq)

46
Q

What is the positive result of a halide test if IODINE is present?

A

Yellow precipitate which is insoluble in concentrated NH3 (aq)

47
Q

Give the ionic equation for reaction of CHLORINE with AgNO3?

A

Ag+ + Cl- -> AgCl

48
Q

Give the ionic equation for reaction of BROMINE with AgNO3?

A

Ag+ + Br- -> AgBr

49
Q

Give the ionic equation for reaction of IODINE with AgNO3?

A

Ag+ + I- -> AgI

50
Q

What is the sequence of tests for anions?

A
  1. Carbonate test
  2. Sulfate test
  3. Halide test
51
Q

Why is carbonate test carried out before the sulfate and halide test?

A

BaCO3 and AgCO3 are both insoluble in water and form precipitates so carbonate ions need to be removed first

52
Q

Why is sulfate test carried out before the halide test?

A

AgSO4 is insoluble in water and will form a precipitate so sulfate ions need to be removed first

53
Q

In a mixture of ions why should HNO3 be used in the carbonate test and not H2SO4 or HCl?

A

Would affect sulfate and halide test otherwise

54
Q

In a mixture of ions why should Ba(NO3)2 be used in the sulfate test and not BaCl2?

A

Would affect halide test otherwise

55
Q

How is the test for ammonium ions, NH4+ carried out?

A

Add NaOH to solution being tested and warm it

56
Q

What is the positive result from ammonium ion test?

A

Moist pH indicator paper will turn blue in the presence of ammonia gas

57
Q

Give the equation for the ammonium ion test?

A

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

(OCR A) A-level Chemistry (21 decks)

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