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CHEMISTRY > CHAPTER 8: REACTIVITY TRENDS > Flashcards

CHAPTER 8: REACTIVITY TRENDS Flashcards

1
Q

What are group 2 elements called?

A

Alkaline earth metals.

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2
Q

Are group 2 elements found in their natural state?

A

No, they are found in compounds because they’re too reactive on their own.

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3
Q

How many electrons do Alkaline earth metals have in their outershell and structurally, where is it found?

A

Alkaline earth metals have 2 electrons on their outer shell which is 2 more than the electron configuration of a noble gas, the two electrons are in the outer s-subshell of the alkaline earth metals.

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4
Q

What happens to metals during redox reactions?

A

Each metal atom is oxidised, loosing two electrons to form 2+ ions with the electron configuration of a noble gas.

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5
Q

What are redox reactions?

A

Reactions where both reduction and oxidation are taking place.

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6
Q

What is the difference between reduction and oxidation?

A

During reduction an atom gains electrons and during oxidation an atom looses electrons. Reduction and oxidation happens at the same time.

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7
Q

Why are group 2 elements called reducing agents?

A

Because they reduce other elements.

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8
Q

What happens in redox reactions with oxygen?

A

Oxygen is reduced(-2) and the metal (+2) is oxidised, the reaction forms a metal oxide.

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9
Q

What is formed and what happens in redox reactions with water?

A

During redox reactions with water, an alkaline hydroxide and hydrogen gas is formed. The reactivity increases down the group and becomes more vigorous. The alkaline metal is fully oxidised but the hydrogen is not fully reduced because hydrogen gains a -1 ion when bonded to a metal instead of a -2 ion.

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10
Q

What happens in redox reactions with dilute acids?

A

The reaction is:
metal + acid —> salt + hydrogen
The reactivity increases down the group
The acid forms a +1 ion and the metal is fully oxidised

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11
Q

What are the rules for oxidation?

A
  • Alkali metals have an oxidation number of +1 alkaline earths are +2
  • All metals have positive oxidation numbers non-metals can have positive or negative oxidation numbers
  • Fluorine has a -1 oxidation number
  • Hydrogen is +1 when bonded to non-metals but -1 when bonded to metals
  • Oxygen is -2 except in peroxides
  • All group 1,2,3 compounds have an oxidation number of +1, +2, +3
  • Chlorine is usually -1
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12
Q

Why does the reactivity increase down group 2?

A

The reactivity increases as the group 2 goes down because as the group goes down the 1st and the 2nd ionisation energy decreases meaning that it is easier for the elements to loose electrons and therefore react as the group goes down.

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13
Q

What do group 2 compounds release and form when they react with water?

A

They release hydroxide ions OH- which form alkaline solutions of the metal hydroxide

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14
Q

Are group 2 hydroxides soluble?

A

Yes, only slightly in water. When the solution becomes saturated any further metal and hydroxide ions will form a solid precipitate

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15
Q

What is qualitative analysis?

A

Analysis that relies on simple observations rather than measurements.

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16
Q

What are the different test for anions?

A

Carbonate test, sulfate test and halide test.

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17
Q

What is the carbonate test?

A
  • In a test tube, add dilute nitric acid to the solid or solution being tested. If bubbles appear, the solution may be a carbonate.
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18
Q

What is the test for carbon dioxide?

A

Bubble the gas through lime water and if CO2 is present a white precipitate will appear. This is because carbon dioxide reacts to form a white precipitate of calcium carbonate which turns the lime water cloudy.

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19
Q

What is the test for sulfates?

A

Add barium ions to the unknown solution and if it has a white precipitate sulfate is present.

20
Q

What are barium ions normally added as?

A

Aqeous barium chloride or aqoeus barium nitride

21
Q

What is the test for Chlorine?

A

Add aqueous silver ions in the form of silver nitrate solutions which would form a white precipitate and add aqueous ammonia which would dissolve the white precipitate.

22
Q

What is the test for Bromide?

A

Add aqeous silver ions in the form of silver nitrate solutions which would result in a cream precipitate then add concentrated aqeuos ammonia which would dissolve the cream precipitate.

23
Q

What is the test for Iodide (I-)?

A

Add aqueous silver ions eg aqueous silver nitrate to the solution which would result in a yellow precipitate then add concentrated aqueous ammonia and it won’t dissolve.

24
Q

What is the correct order for test for anions?

A

CASH
Carbonate
sulfate
halide

This is because barium carbonate and silver sulfate are both insoluble so they can give precipitates and give misleading results.

25
Q

What test do you need to know for cations?

A

Ammonium

26
Q

What is the test for ammonium?

A

Add dilute sodium hydroxide and warm it and test any gas produced with damp red litmus paper. The litmus paper will turn blue if ammonia gas is present.

27
Q

How do group 2 oxides react with water?

A

A hydroxide is formed and the PH of these hydroxides is greater than 7 because they are alkaline. Down the group the hydroxides get more soluble and therefore more alkaline

28
Q

What are some uses of group 2 compounds?

A
  • Calcium hydroxide is used to neutralise acidic soils
    Ca(OH)2 + 2HCL —> CaCl2 + 2H20
    -Magnesium hydroxide (same equation as calcium hydroxide) and calcium carbonate are used as antacid which is used in indegestion remedies to remove excess stomach acids.

CaCO3 + 2HCL —> CaCl2 +H2O+ CO2

29
Q

What type of molecules do halogens occur as?

A

Diatomic molecules

30
Q

What are diatomic molecules?

A

Molecules that contain two chemically bonded atoms

31
Q

What type of bonds do the halogens form?

A

Simple covalent lattices

32
Q

Why does the melting and boiling point of group 17 increase as you go down the group?

A

Because to break the lattice down we have to overcome the induce dipole-dipole forces between the molecules. As the number of the electrons increases these induced dipole-dipole forces get stronger. When we break down molecules in the forces we don’t breakdown the covalent bonds but we breakdown the induced dipole-dipole forces/ london forces.

33
Q

What is a dipole?

A

A separation in charge so that one end of a polar molecule has a small positive charge and the other end has a small negative charge.

34
Q

What is a polar molecule?

A

A molecule with a positive and negative charge at the ends of the molecule.

35
Q

What are induced dipoles?

A

They are weak intermolecular forces caused by attractions between very small dipoles in molecules.

36
Q

What is an induced dipole-dipole interaction?

A

Attractive forces between induced dipoles in different molecules.

37
Q

What are the chemical properties of halogens?

A
  • They have the outer shell configuration of s2 p5
  • 7 outer shell electrons
  • They accept 1 electron on their outer shell making it become 1- halide ions
  • They are oxidising agents because they accept electrons however their oxidising power decreases down the group.
38
Q

What is the procedure for halogen-halide displacement reactions?

A
  • A solution of a halogen is added to a solution of a halide ion. If the halogen is more reactive it displaces the less reactive halide.
  • The colour of the test tube indicates which halogen is present and a small amount of organic solvent is added to make the halogen identification easier.
39
Q

What are the colours of the halogens in water and an organic solvent?

A

Cl2- Very pale green in water and organic solvent
Br2- Yellow in water and orange in organic solvent
I2- Pale brown in water and violet in organic solvent

40
Q

What are the uses of chlorine?

A
  • Added to drinking water to kill harmful bacteria eg cholera(the bacteria is killed by the chlorate 1 ion
    Cl2 (aq) +H20(l) —-> HCl (aq) + HClO (aq)
  • Reacts with cold dilute sodium hydroxide to make bleach
    Cl2 + 2NaOH(aq) —> NaCl(aq) + NaClO + H2O
  • These are examples of disproportionation.
41
Q

What is disproportionation?

A

When the same element is oxidised and reduced

42
Q

What are arguments for the chlorination of water?

A
  • Kills harmful bacteria so reduces the risk of waterborne diseases such as cholera
  • Prevents algae growth in water
  • Eliminates bad smell/taste in water
  • It persist in water so its longer lasting than alternatives such as ozone
43
Q

What are some arguments against the chlorination of water?

A
  • Chlorine is toxic and a respiratory irritant
  • Chlorine reacts with organic matter in water to form chlorinated hydrocarbons (carcinogens) (which cause cancer)
  • Some people are against government intervention
44
Q

How do chloride ions react with silver ions?

A

Ionic equation: Ag+(aq) + Cl(aq) —> AgCl (s)
White precipitate
Soluble in dilute ammonia

45
Q

How do Bromine ions react with silver ions?

A

Ionic equation: Ag+(aq) + Br-(aq) —> AgBr(s)
Cream precipitate
Partially soluble in dilute ammonia fully soluble in concentrated ammonia

46
Q

How do Iodine ions react with silver ions?

A

Ionic equation: Ag+(aq) + I-(aq) —> AgI(s)
Yellow precipitate
Insoluble in both dilute and concentrated ammonia

47
Q

What are the three steps to calculating oxidation numbers?

A

CHEMISTRY (7 decks)

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