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CHEM PAPER 1 > REACTIVITY TRENDS > Flashcards

REACTIVITY TRENDS Flashcards

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1
Q

What happens to ionisation and reactivity as you move down group 2

A

First ionisation energy decreases as atomic radius increases and so reactivity increases as outer electrons are further from the nucleus so attraction is weaker

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2
Q

What happens to nuclear charge as you move down groups and how does this affect ionisation

A

number of protons in the atom will increase down the group, so nucleus will become more positively charged, however as the atomic radius increases as number of electron shells increases, this overrides the effect of the increased nuclear charge and ionisation energy will still decrease

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3
Q

what happens group 2 metals react with water

A

they form bases, metal hydroxides in particular

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4
Q

reactions with water down group 2

A

More reactivity, as atoms are larger so more electron shielding

BERYLIUM DOES NOT REACT WITH WATER

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5
Q

What happens when magnesium reacts with steam

A

will form magnesium oxide and will react vigorously

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6
Q

what happens when Group 2 elements react with oxygen

A

they are oxidised (obviously) and will form metal oxides in a redox reaction

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7
Q

state of group 2 oxides and what happens when they react with water

A

they are white solids

form bases when added to water (hydroxides)

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8
Q

Group 2 hydroxide trends down the group

A

become more strongly alkaline as they become more soluble and OH- ions are more likely to be released

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9
Q

Neutralisation and example of a group 2 oxide and hydroxide with acid

A

will form a group 2 salt and water

CaO + 2HCl –> CaCl2 + H2O

Ca(OH)2 + H2SO4 –> CaSO4 + 2H2O

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10
Q

Use of a group 2 hydroxide in nature

A

Calcium hydroxide is used to neutralise acidic soils to allow some crops or plants to grow if the pH is too low

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11
Q

Use of a group 2 hydroxide in medicine

A

Magnesium hydroxide is used to neutralise excess stomach acid as will react to form water and a magnesium salt

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12
Q

Trend of boiling points effect on states down group 7

A

Boiling point increases as London forces increase due to increasing size and mass of atoms

and so physical state goes from gas down to solid as you move down

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13
Q

Electronegativity trend down group 7

A

decreases as the atoms get larger so electron shielding increases so ability to attract electrons in a covalent bond will decrease

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14
Q

How can displacement reactions of halogens be observed

A

hexane is added to the aqueous solution and the halogen will dissolve readily in the solvent causing a coloured organic layer to form above the aqueous layer

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15
Q

how are halide ions displaced

A

more reactive halogen will displace less reactive halide ions

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16
Q

Reactivity of halogens down the group

A

decreases as for a reaction to occur the halogen will need to gain an electron, as electronegativity decreases down the group, so does reactivity

HALOGENS ARE LESS OXIDISING AS YOU MOVE DOWN THE GROUP AS THEY ARE LESS READILY REDUCED

17
Q

Reaction of KCl and Cl2 and colour changes

A

no reaction, aqueous and organic solution are both colourless

18
Q

Reaction of KBr and Cl2 and colour changes

A

Chlorine will displace the bromide ions

aqueous solution will turn yellow and the organic solution will turn orange

19
Q

Reaction of KI and Cl2 and colour changes

A

Chlorine will displace iodide ions

aqueous solution will go brown and organic layer will be purple

20
Q

Reaction of KCl / KBr and Br2 and colour changes

A

no reaction

aqueous solution will be yellow and organic layer will be orange

21
Q

KI and Br2 reaction

A

Bromine will displace iodide ions

aqueous will be brown and organic layer will be purple

22
Q

Reaction of I2 with KCl, KBr, KI

A

no reactions

aqueous solution will be brown and organic layer will be purple

23
Q

How to test for halides and corresponding precipitates

A

Add dilute HNO3 and then AgNO3, the precipitate colour will help identify the halide ion

Cl- will give a white precipitate (AgCl)

Br- will give a cream precipitate (AgBr)

I- will give a yellowy precipitate (AgI)

24
Q

Why is HNO3 added when testing for halides

A

to react with any other anions other than halides (to prevent false results)

25
Q

How to FURTHER TEST for halide ions

A

add ammonia solution to precipitates obtained

Cl- precipitate dissolves in dilute NH3

Br- precipitate dissolves in concentrated NH3

I- precipitate is insoluble in concentrated NH3

26
Q

How is bleach made and show equation

A

a disproportionation reaction

mix chlorine with sodium hydroxide forms sodium chlorate(1)

2NaOH + Cl2 –> NaClO + NaCl + H2O

27
Q

What is a disproportionation reaction

A

One in which an element has been simultaneously reduced and oxidised

28
Q

Uses of bleach

A

Adding chlorine to water produces chlorate ions which kill bacteria

Can be used to bleach fabrics to remove colour

used as a cleaning agent

29
Q

Water sterilisation reactions

A

H2O + Cl2 –> HCl + HClO

HClO + H2O <–> ClO- + H3O+

30
Q

Advantages and disadvantages to chlorinating drinking water

A
  • Kills microorganisms that cause disease
  • long lasting so reduces build up of bacteria further down supply
  • reduces growth of algae
  • chlorine gas is toxic
  • liquid chlorine causes sever chemical burns
  • chloroalkanes could form which are linked to causing cancer
31
Q

Ethical issues with chlorination water and alternatives for water sterilization

A

Some claim it is forced medication to whole population

ozone is a powerful [O] that kills microorganisms, it is expensive to produce and has short half life

UV light damages DNA of microorganisms, but is ineffective in cloudy water and wont prevent further contamination

32
Q

Test for ammonium compounds

A

add NaOH and gently heat, ammonia will be produced if present

use damp red litmus, ammonia will dissolve in water and turn litmus blue

33
Q

test for hydroxides

A

As they are alkaline, they turn red litmus paper blue

34
Q

Test for carbonates

A

add acid, which should make CO2, when bubbled through limewater it will turn cloudy

35
Q

test for sulfates

A

add hydrochloric acid to remove carbonates

add barium chloride, barium sulphate should be produced and so will see a white precipitate

36
Q

Order or testing for carbonates, sulphates, halides

A

test for CO2 first, then add barium chloride to test for sulphates, then silver nitrate to test for halides

37
Q

Neutralisation and example of a group 2 oxide and hydroxide with acid

A

will form a group 2 salt and water

CHEM PAPER 1 (15 decks)

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