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Chemistry A-level > Chapter 8 > Flashcards

Chapter 8 Flashcards

1
Q

Why are group 2 elements reducing agents?

A

Because they lose their outer S2 electrons to form 2+ ions.

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2
Q

What is happens to reactivity of group 2 elements.

A

Reactivity increases down the group.

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3
Q

Which group 2 metals react with oxygen and to form what?

A

All group 2 metals react with oxygen to produce metal oxide.

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4
Q

Which group 2 metals react with water and to form what?

A

Group 2 metals generally react with water to form metal hydroxides and hydrogen.

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5
Q

What redox reactions happen with group 2 elements?

A

group 2 elements and dilute acid to produce a salt and hydrogen.

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6
Q

What happens to first & second ionisation energy for group 2 elements? why?

A

It decreases down the group

  • the outermost electrons are held more weakly as they are further away from the nucleus - weakens the attraction
  • the outer shell/ electrons become more shielded from the attraction of the nucleus by the repulsion force of inner shell electrons
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7
Q

What happens when group 2 elements react with water?

A

form group 2 metal hydroxides

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8
Q

What is formula of hydroxide for Mg?

A

Mg(OH)2

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9
Q

What is the trend of metal 2 hydroxides down the group?

A
  • solubility increases down the group, resulting in solutions that contain more OH- ions, hence an increase in alkalinity , ph. also increases from 10 to 12
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10
Q

What three types of group 2 act as bases?

A
  • group 2 hydroxides, carbonates and oxides
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11
Q

What is Ca(OH)2 used for?

A

It used in agriculture to neutralise acidic soils to help maintain an optimum ph for crops.

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12
Q

What is CacO3 and Mg(OH)2 used for?

A

Used as an ‘antacid’ to neutralise excess hydrochloric acid during indigestion.

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13
Q

What are group 7 elements known as?

A

Halogens

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14
Q

Which block of the periodic table is where group 7 elements are?

A

Part of p-block.

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15
Q

What 4 things increase down group 7?

A
  • nuclear charge
  • no. of electrons
  • atomic radius
  • boiling point
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16
Q

What happens to reactivity down group 7?

A

Reactivity decreases down the group.

17
Q

What happens when more electrons are added down the group?

A
  • The strength of the temporary dipoles increases

- Increased dipoles mean greater London forces, leading to an increase in melting and boiling point.

18
Q

Why are group 7 elements can be oxidising agents?

A

Because they often gain an electron to form a 1- halide ion.

19
Q

How do halogens displace each other?

A

A higher up and more reactive halogen will displace a less reactive halide ion from a solution.

20
Q

How can you tell a halogen displacement has taken place?

A

A colour change

21
Q

What happens to group 7 elements down a group?

A

Down the group, the increase in atomic radii and shielding outweighs the increase in nuclear charge, so electronegativity decreases.

22
Q

What happens when electronegativity decrease?

A

Electronegativity decreases down a group, reduces a halogen’s ability to attract an electron and form a 1- ion, hence it’s reactivity.

23
Q

What is a disportionation reaction?

A

Is where a single element is simultaneously reduced and oxidised in a reaction.

24
Q

Give an example of a disportionation reaction?

A

Chlorine when added to water. Cl2 + H2O to HCL + HClO

Chlorine 0 then HCl is -1 then HClO is +1

25
Q

What is chlorine used in?

A

It is used in water purification and water treatment.

26
Q

What are the advantages of chlorinating water?

A
  • sanitises water by killing bacteria

- prevents the spread of waterborne diseases

27
Q

What are the disadvantages of chlorinating water?

A
  • may react with hydrocarbons to form carcinogenic chlorated hydrocarbons
  • Cl2 is a toxic gas can irritate the respiratory systems in low concentrations
28
Q

What is the test for halide ions (anions)?

A
  • Add aqueous Ag+ ions from AgNo3

- Nh3 can be added to help distinguish between what halide ions are there

29
Q

Colour and solubility of ammonium of chloride, bromine and iodide for the test for halide ions?

A

Chloride - white precipitate & soluble in dilute in NH3
Bromide- cream precipitate & soluble in conc. in NH3
Iodide- yellow precipitate & soluble in conc. in NH3

30
Q

What is the test for carbonate?

A
  • Add any dilute acid and observe effervescence

- Bubble gas through limewater to test for CO2- will turn cloudy

31
Q

What is the test for sulfate?

A
  • Add an excess of Ba(No3)

- If sulfate is present, a white precipitate will be formed.

32
Q

What is the sequence of tests?

*why?

A
  1. Carbonate
  2. Sulfate
  3. Halides
33
Q

What is the test for cations?

A
  • Add NaOH & heat gently

- Ammonia gas can be identified by litmus paper turning red.

Chemistry A-level (14 decks)

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