Group 1, the alkali metals

Question 1

describe the physical appearance of alkali metals

Answer 1

soft, easily cut and shiny

Question 2

what is the oxidation state of Group 1 metals in their compounds ?

Answer 2

+ 1

Question 3

what is the reaction with water - lithium

Answer 3

reacts steadily with cold water given off

Question 4

what is the reaction with water - sodium

Answer 4

melts and bubbles

Question 5

what is the reaction with water - potassium

Answer 5

melts and bubbles

Question 6

write the balanced equation for the reaction between lithium and water

Answer 6

2Li (s) + 2H2O -> 2LiOH (aq) + H2
(g)

Question 7

write the balanced equation for the reaction between potassium and chloride

Answer 7

2K (s) + CI2 (g) -> 2KCI (s)

Question 8

describe the trend in solubility of the hydroxides down Group 1

Answer 8

increases down the group

Question 9

strong base - define

Answer 9

they are fully ionised in water giving solutions that contain OH-ions

Question 10

what are the two unusual features of Group 1 carbonates

Answer 10

dissolve in water
do not decompose on heating except lithium carbonate

Question 11

describe what happens when sodium and potassium nitrates are heated

Answer 11

first melt and then on stronger heating start to decompose, giving of oxygen, only decompose till nitrates

Question 12

write the balanced equation for the thermal decomposition potassium nitrate and oxygen

Answer 12

2KNO3 (s) -> 2KNO2 (s) + O2 (g)

Question 13

write the balanced equation for the thermal decomposition lithium nitrate into lithium oxide, nitrogen dioxide and oxygen

Answer 13

LiNO3 (s) -> 2LiO (s) + 4NO2 (g) + O2 (g)

Question 14

give 3 reasons why compounds of sodium and potassium are widely used as chemical reagents

Answer 14

• ions of alkali metals are unreactive so they act as spectator ions
• most sodium and potassium compounds are soluble in water
• the ions of alkali metals are colourless in aqueous so they o not hide or interfere with colour changes

Question 15

flame colours
lithium
sodium
potassium

Answer 15

lithium - bright red
sodium - bright yellow
potassium - lilac

Question 16

describe how to conduct a flame test

Answer 16

1. moisten a nichrome wire with concentrated HCI
2. dip the wire into the sample
3. hold the wire in a blue Bunsen burner flame

Question 17

why do we dip the nichrome wire into HCI before dipping into the sample ?

Answer 17

solid salt is converted into more volatile metal chlorides - turns solid to gas so easier to observe

Question 18

what does not burn during flame tests ?

Answer 18

ionic compounds such as NaCI

Question 19

explain the origins of flame colour

Answer 19

thermal energy from excites the outer electrons of the metal ions promoting them to higher energy levels drop - radiation emitted in visible region of the spectrum

Question 20

suggest why Be and Mg produce no flame colour

Answer 20

radiation emitted is not visible region of the spectrum