Groups one and two

Question 1

outer shell electrons in gr2

Answer 1

2

Question 2

going down the groups, metals become more reactive reason

Answer 2

although the nuclear charge increases down the group, there is increased shielding and a larger distance between the outermost electron and nucleus which cause a weak attraction that outweighs having a high nuclear charge

Question 3

reactivity increases down groups

Answer 3

easier for atoms to lose electrons

increasingly vigorous reactions caused

Question 4

reactions of group 2 metals with oxygen

Answer 4

2M (s) + O2 (g) → 2MO (s)

Sr and Ba also form a peroxide (MO2)

Question 5

reactions of all metals with water

Answer 5

M (s) + 2H2O (l) → M(OH)2 (s) + H2 (g)

Except for, Be which does not react with water

Question 6

what type of solution do the reactions with water create

Answer 6

alkaline (presence of OH)

Question 7

reactions with chlorine

Answer 7

Mg (s) + Cl2 (g) → MgCl2 (s)

Question 8

what happens to the solutions formed with water when going down the group

Answer 8

becomes more alkaline

Question 9

what is calcium hydroxide

Answer 9

limewater

Question 10

reactions of group 2 oxides with sulfuric acid

Answer 10

insoluble sulphates form at the surface of the oxide so solid underneath cant react with acid.

oxide + dilute sulfuric acid → sulfate + water

Question 11

reaction of group 2 hydroxide and HCl/SO4

Answer 11

colourless solutions of metal salts.

sulphates decrease in solubility down group

Hydroxides still increase

hydroxide + dilute hydrochloric acid → chloride + water

hydroxide + dilute sulfuric acid → sulfate + water

Question 12

group 2 hydroxides trend in alkalinity

Answer 12

become more alkaline down the group

he higher the concentration of OH- ions formed, the more alkaline the solution

The alkalinity of the formed solution can therefore be explained by the solubility of the Group 2 hydroxides

Question 13

GROUP 2 hydropxides solubility and alkalinity _____
down the group

Answer 13

INCREASES

Question 14

GROUP 2 sulfates solubility _____
down the group

Answer 14

decreases

(alkalinity not affected as no OH)

Question 15

thermal decomposition

Answer 15

the breakdown of a compound into two or more substances using heat

Question 16

only group 1 carbonate that decomposes

Answer 16

lithium -

rest of the group 1 carbonates cant decompose at bunsen temps

Question 17

carbonate decompose equation

Answer 17

XCO3 (s) rightwards arrow with HEAT on top XO (s) + CO2 (g)

Question 18

only nitrate G1 that will decompose to form nitrogen dioxide

Answer 18

lithium nitrate LiNO3

4LiNO3 (s) rightwards arrow with HEAT on top 2Li2O (s) + 4NO2 (g) + O2 (g)

Question 19

what happens in decomposition of group 1 nitrastes except lithium

Answer 19

dont decompose fully and produce metal nitrite and oxygen

2XNO3 (s) rightwards arrow with HEAT on top 2XNO2 (s) + O2 (g)

Question 20

group 1 nitrate decomposition gets more difficult

Answer 20

higher temps needed

Question 21

Since the formed nitrogen dioxide gas is toxic

Answer 21

store in fume cupboard

Question 22

The general equation for the decomposition of Group 2 nitrates is:

Answer 22

X(NO3)2 rightwards arrow with HEAT on top XO + 1 halfO2 + 2NO2

Question 23

thermal stability of group 1 and 2 nitrates and carbonates increases down the group

Answer 23

smaller ions at top of group are more polarising of the anions

smaller cation attracts delocalided electron in the carbonate towards itself

the higher the charge and smaller ion = more polarising

more polarised = more likely to thermally decompose as bonds in carbponate and nitrate are weaker

down group ions become larger
lower charge density
less distorting
less likely to thermally decompose

Question 24

flame test method

Answer 24

Dip the loop of an unreactive metal wire such as nichrome or platinum in concentrated acid, and then hold it in the blue flame of a Bunsen burner until there is no colour change

This cleans the wire loop and avoids contamination

This is an important step as the test will only work if there is just one type of ion present

Two or more ions means the colours will mix, making identification erroneous

Dip the loop into the solid sample and place it in the edge of the blue Bunsen flame

Avoid letting the wire get so hot that it glows red otherwise this can be confused with a flame colour

Question 25

flame test results

Answer 25

Li red
Na strong persistent yellow-orange
K lilac (pink)
Rb red (reddish-violet)
Cs blue-violet (see below)
Ca orange-red
Sr red
Ba pale green
Cu blue-green (often with white flashes)
Pb greyish-white