4- Inorganic chemistry and the periodic table

Question 1

Define thermal decomposition.

Answer 1

A reaction in which a compound breaks down under heating,

Question 2

Group 1 metals are powerful ______ _______?

Answer 2

Reducing agents.

Question 3

For group one, what is the trend in reactivity down the group?

Answer 3

Increases.

Question 4

Give 3 reasons why sodium and potassium are used regularly as chemical reagents?

Answer 4

1. Ions of Group one metals are fairly unreactive so act as spectator ions.
2. Most of their compounds are soluble in water, including hydroxides and carbonates.
3. Ions are colourless in aq sol. so don’t interfere with or hide colour changes.

Question 5

Explain steps for a flame test of group one metals.

Answer 5

Dip nichrome wire in concentrated HCl, as chlorides evaporate easier so flames are coloured more strongly. Then, dip wire in sample crystals. Finally, place wire in Bunsen flame,

Question 6

What colour are Lithium ions in a flame test?

Answer 6

Bright red.

Question 7

What colour are Sodium ions in a flame test?

Answer 7

Bright yellow.

Question 8

What colour are Potassium ions in a flame test?

Answer 8

Lilac.

Question 9

Group two compounds are _________ in water.

Answer 9

Insoluble.

Question 10

Group 2 metals are _______ _______ ?

Answer 10

reducing agents

Question 11

Describe the reaction of group 2 elements with oxygen.

Answer 11

Form white ionic oxides of M2+ and O2-.

Question 12

What colour flame does Magnesium cause when burnt in oxygen?

Answer 12

White.

Question 13

What colour flame does Calcium cause when burnt in oxygen?

Answer 13

Red.

Question 14

What colour flame does Barium cause when burnt in oxygen?

Answer 14

Green.

Question 15

Compound formed when Barium is burnt in oxygen?

Answer 15

Barium peroxide.
BaO2.

Question 16

Explain the reaction of Magnesium with water.

Answer 16

Magnesium reacts slowly in cold water producing Mg(OH)2
Reacts much quicker heated in steam and produces MgO and H2 gas.

Question 17

Reaction of Calcium and cold water?

Answer 17

Ca(OH)2 and H2 gas.

Question 18

Barium with water?

Answer 18

Reacts quickly and it hydroxide is more soluble.

Question 19

Group two reaction with chlorine?

Answer 19

On heating:
M(s) + Cl2 (g) –> MCl2 (s)

Question 20

Solubility of group two oxides? (M(OH)2)

Answer 20

Increases down the group

Question 21

What does calcium hydroxide form when dissolved in water?

Answer 21

Limewater.

Question 22

Equation for limewater test for carbon dioxide?

Answer 22

Ca(OH)2 + CO2 -> CaCO3 +H2O

Question 23

General trend for solubility of G2 compounds?

Answer 23

If both ions are small or both ions are big, they tend to be insoluble.

Question 24

Which group 2 hydroxide is most soluble?

Answer 24

Barium hydroxide

Question 25

Barium carbonate is ________ in water?

Answer 25

insoluble

Question 26

Properties of group 2 carbonates?

Answer 26

Insoluble in water, react with dilute acids, decompose on heating.

Question 27

General equation for decomposition of G2 carbonates on heating?

Answer 27

MCO3 -> MO(s) + CO2(g)

Question 28

Trend in ease of decomposing?

Answer 28

Harder to decompose down the group. More thermally stable.

Question 29

Properties of G2 Nitrates?

Answer 29

All have formula M(NO3)2. Colourless crystalline solids , very soluble in water. Decompose to form oxide when heating (MO). They become more difficult do decompose down the group.

Question 30

Equation for decomposing of G2 nitrates?

Answer 30

2M(NO3)2 (s) ->2MO (s) + 4NO2 (g) + O2(g)

Question 31

Properties of G2 sulfates?

Answer 31

All colourless solids with formula MSO4. Become less soluble down the group.

Question 32

Test for sulfate ions?

Answer 32

Add barium chloride or barium nitrate (Ba2+) to acidified solution. White precipitate should form. Ba2+ + SO4 2- -> BaSO4 (s)

Question 33

Flame colour of Beryllium and Magnesium?

Answer 33

No colour

Question 34

Flame colour of Calcium?

Answer 34

Brick red

Question 35

Flame colour of Strontium?

Answer 35

Bright red

Question 36

Flame colour of Barium?

Answer 36

Pale green

Question 37

Trend in thermal stability for G1 and G2 nitrates and compounds? Explain

Answer 37

More stable down the group. This is because the larger positive ions have a lower charge density, and therefore distorts the carbonate/ nitrate ion less, making it more stable. G2 less stable generally than G1.

Question 38

G7 London forces trend and why. Melting temp?

Answer 38

Increase down group as more electrons. MP rises down group.

Question 39

Chlorine oxidation state and exceptions?

Answer 39

Normally -1 but can be positive if oxidised by oxygen and fluorine.

Question 40

Halogens solubility?

Answer 40

More soluble in organic solvents than water.

Question 41

What determines if phosphorous and chlorine make PCl3 or Pcl5?

Answer 41

Whether Chlorine gas is in excess or not.

Question 42

Determining which halide?

Answer 42

AgNO3 added to solution of halide ions. Chloride turns white Bromide turns Cream iodide turns Yellow.

Question 43

Reaction of NaCl in conc. H2SO4?

Answer 43

HCl fumes form, NaHSO4 remains. Cl is the weakest reducing agent (strongest [O] most likely to form negative ions) .No redox, just acid base.

Question 44

Reaction of NaBr in conc. H2SO4?

Answer 44

Br2 vapour (orange) and SO2 gas form (colourless). Some HBr forms, Solid NaHSO4 formed. Redox reaction, Br has some reducing power (is oxidised itself to Br2 from Br-). Sulfur is reduced from +6 to +4. Also acid base (HBr formed).

Question 45

Reaction of NaI in conc. H2SO4?

Answer 45

Dark solid of I2 forms which gives off purple vapour when heated. Some Sulfur is formed and H2S is formed. Redox reaction, Iodine reduces Sulfur to 0 in S and 2- in H2S.

Question 46

Hydrogen halides properties?

Answer 46

Colourless gas at room temp. Very soluble in water, ionise completely. Strong acids.

Question 47

HX with NH3?

Answer 47

White smoke of ammonium salt. NH4 (+)X(-) (s).

Question 48

Cl2 and Br2 reaction with water?

Answer 48

H20 + X2 -> HXO (aq) + Hx(aq) Disproportionation. Reversible. Greater reaction with Cl than Br. Iodine insoluble in water, barely reacts.

Question 49

Reaction of Cl2 in Sodium or potassium hydroxide?

Answer 49

Cl2 + 2OH- -> ClO- + Cl- + H2O(l)

Question 50

Heating of Chlorate (I) ions?

Answer 50

Disproportionation. 3ClO- -> ClO3- + 2Cl-

Question 51

Overall equation for reaction of Chlorine with hot potassium hydroxide? How do bromine and iodine react?

Answer 51

3Cl2 + 6OH- -> ClO3- +5Cl- +3H20 Similarly, but their XO- ions are less stable so disproportionate at a lower temp.