inorganic chemistry and the periodic table

Question 1

when group 2 elements react, they….

Answer 1

lose 2 electrons to form +2 ions, allowing them to achieve a full outer shell.

Question 2

down group 2 the atomic radius…

Answer 2

increases, due to additional electron shells

Question 3

the reactivity of group 2 elements down a group…

Answer 3

increases due to increased electron shielding and increased atomic radius, making their outer electrons easier to lose.

Question 4

first IE down group 2

Answer 4

decreases due to a greater atomic radius and increased shielding. this makes it easier to remove an electron

Question 5

reactions of group 2 elements with water (liquid)

Answer 5

produces a metal hydroxide and hydrogen gas.
Mg + 2H2O(l) -> Mg(OH)2 + H2

Question 6

reactions of group 2 elements with water (steam, gas)

Answer 6

produces a metal oxide and hydrogen gas.
Mg + H2O(g) -> MgO + H2

Question 7

reactions of group 2 elements with chlorine.

Answer 7

forms a metal chloride, which are all white precipitates.
as you move down the group the reactions become more vigorous as the elements are more reactive.

Question 8

reactions of group 2 elements with oxygen.

Answer 8

Produces solid white metal oxides. Sr and Ba can be reacted with excess o2 and heat energy to form metal peroxides.
2M + O2 -> 2MO

Question 9

reactions of group 2 elements with dilute acids

Answer 9

produces bubbles of hydrogen gas and solutions of metal compounds.
X + HCl -> XCl2 + H2

Question 10

reactions of group 2 hydroxides with dilute acid

Answer 10

group 2 hydroxides react with dilute acid to form salt and a water.
- called a neutralisation reaction.
. HCl forms chloride salts
. SO4 forms sulfate salts
. NO3 forms nitrate salts

Question 11

Solubility of group 2 hydroxides

Answer 11

Increases down the group, (Mg(OH)2) is the least soluble and (Ba(OH)2) is the most soluble.

Question 12

Solubility of group 2 sulfates

Answer 12

Solubility decreases down the group meaning (Mg(SO4) is the most soluble and (BaSO4) is the least soluble.

Question 13

BaCl2 is used as a test for…

Answer 13

sulfate ions.
white precipitate formed when sulfate ions are present.

Question 14

Thermal decomposition of group 2 metals

Answer 14

group 2 carbonates and nitrates undergo thermal decomposition to produce solid metal oxides and a variety of gases.
this is done by simply heating the substance in aerobic conditions (plenty of oxygen)

Question 15

Group 2 carbonates produce

Answer 15

carbon dioxide and a metal oxide
XCO3 -> XO + CO2

Question 16

thermal decomposition of group 2 carbonates as ions increase in size

Answer 16

as you go down group 2, more heat is required for this reaction as the ions increase in size and the carbonates increase in thermal stability.

Question 17

group 2 nitrates produce…

Answer 17

nitrogen dioxide and oxygen along with the white powdered metal oxide
eg: 2X(NO3)2 -> 2XO + 4NO2 + O2
as you go down group 2, more heat is required for this reaction as the ions increase in size and the nitrates increase in thermal stability.

Question 18

thermal decomposition of group 1 metals.

Answer 18

group 1 carbonates and nitrates also undergo thermal decomposition upon heating in aerobic conditions.
e.g: 4LiNO3 -> 2Li2O + 4NO2 + O2

Question 19

explanation of thermal stability trend…g1&g2

Answer 19

elements of group 1 & 2 form more stable carbonates and nitrates as you go down their groups, and so require more heat energy to undergo thermal decomposition.

Question 20

smaller ions have a higher…

Answer 20

charge density

Question 21

smaller ions have a higher…

Answer 21

charge density

Question 22

flame test procedure

Answer 22

Nichrome wire dipped in HCl to clean the wire, nichrome wire dipped into metal compound and is placed over the flame. observe the colour produced.

Question 23

lithium flame colour

Answer 23

red

Question 24

sodium flame colour

Answer 24

yellow-orange

Question 25

potassium flame colour

Answer 25

lilac

Question 26

Magnesium flame colour

Answer 26

Colourless

Question 27

strontium flame colour

Answer 27

Crimson red

Question 28

calcium flame colour

Answer 28

Brick red

Question 29

barium flame colour

Answer 29

pale green

Question 30

how coloured flames are seen…

Answer 30

electrons exist in orbitals and when energy (eg bunsen burner flame) is absorbed by the electrons, some electrons will be promoted to orbitals which have a higher energy level. the electrons will then drop back to their original orbital, the energy emitted may not have a wavelength in the visible light part of the electromagnetic spectrum, which explains why not all atoms and ions produce a colour in the flame test (eg Mg)

Question 31

group 7 elements are highly…

Answer 31

reactive non metals.

Question 32

atomic radius of group 7 elements down the group…

Answer 32

increases due to additional electron shells.

Question 33

melting and boiling point of group 7

Answer 33

they’re simple covalent molecules, held by van der waals forces.
the strength of these forces increases as the Ar of the molecule increases.

therefore the strength of van der waals forces increases down the group, requiring more energy to overcome them, resulting in higher melting and boiling points.

Question 34

reactivity of group 7 elements

Answer 34

group 7 elements need to gain an electron in order to react.

as atomic radius increases,this becomes harder as the positive attraction of the nucleus is weakened by additional shielding.

therefore for group 7’s it’s harder to attract an electron so reactivity decreases down a group.

Question 35

Oxidising power of the halogens.

Answer 35

the halogens act as good oxidising agents as they accept electrons from the species being oxidised and reduced.
this oxidising power decreases down the group as their ability to attract electrons decreases down the group as their ability to attract electrons decreases due to shielding and a greater atomic radius.

Question 36

halide ions are good…

Answer 36

reducing agents as they donate electrons to the species being reduced and are themselves oxidised.

Question 37

hydrogen halides react with ammonia gas to form…

Answer 37

ammonium salts

Question 38

hydrogen halides react with water to form…

Answer 38

dilute acids. in solution, these strong acids disassociate to release their halide ions and hydrogen ions.

Question 39

test for anions - sulfate (SO4 2-)

Answer 39

acidified BaCl2 which reacts to form a white precipitate of barium sulfate.
eg. BaCl2 + XSO4 -> BaSO4 + XCl2

Question 40

test for anions - carbonate (CO3 2-) and hydrogencarbonate (HCO3 2-)

Answer 40

when acid such as HCl is added, the substance containing the carbonate ions will fizz and CO2 gas is given off.
this gas can be bubbled through limewater which will turn cloudy, confirming that its CO2.
eg. XCO3 + 2HCl -> CO2 + H2O + XCL2

Question 41

test for cations - ammonium (NH4 +)

Answer 41

adding NaOH and gently warming, results in the formation of ammonia gas which is basic, therefore the presence of ammonium ions can be tested using damp red litmus paper.
it will turn blue if ammonium ions are present.