Suggested Answers on Note (Chapter 29) P.6 - 7

 

1.     Zinc sulphate

        a)        soluble in water and give a colourless solution

        b)        sample solution: add sodium hydroxide solution Þ white ppt.

        c)        white ppt. redissolve in excess sodium hydroxide solution

        d)        sample solution: add ammonia solution Þ white ppt.

        e)        white ppt. redissolve in excess ammonia solution Þ Zn²⁺ exists

        f)        sample solution: add barium chloride / barium nitrate solution Þ white ppt.

        g)        white ppt. does not dissolve in dilute hydrochloric acid Þ SO₄^2- exists

 

2.        Potassium carbonate

        a)        soluble in water and give a colourless solution

        b)        sample solution: add sodium hydroxide solution Þ no ppt.

        c)        sample solution: add ammonia solution Þ no ppt. Þ Na⁺ or K⁺

        d)        flame test on solid sample Þ lilac flame / violet flame Þ K⁺ exists

        e)        add dilute hydrochloric acid on solid sample Þ colourless gas

        f)        colourless gas turn lime water milky Þ SO₃^2- or CO₃^2-

        g)        colourless gas does not turn the colour of Cr₂O₇^2-/H⁺ Þ CO₃^2- exists

 

3.        Copper(II) chloride

        a)        soluble in water and give a blue solution Þ some coloured ions exist

        b)        sample solution: add sodium hydroxide solution Þ blue ppt.

        c)        blue ppt. does not redissolve in excess sodium hydroxide solution

d)        sample solution: add ammonia solution Þ blue ppt.

        e)        blue ppt. redissolve in excess ammonia solution Þ Cu²⁺ exists

        f)        sample solution: add dilute silver nitrate solution Þ white ppt.

        g)        white ppt. redissolve in dilute ammonia solution Þ Cl^- exists

 

4.        Ammonium iodide

        a)        soluble in water and give a colourless solution

        b)        sample solution: add sodium hydroxide solution Þ no ppt.

c)        sample solution: add ammonia solution Þ no ppt.

        d)    no special flame colour in flame test

e)        heat the solid sample with calcium hydroxide powder Þ pungent smell gas evolved Þ turn wet red litmus paper blue Þ NH₄⁺ exists

        f)        sample solution: add dilute silver nitrate solution Þ yellow ppt.

        g)        yellow ppt. does not dissolve in concentrated ammonia solution Þ I^- exists

 

5.     Iron(II) bromide

        a)        soluble in water and give a green solution Þ some coloured ions exist

        b)        sample solution: add sodium hydroxide solution Þ green ppt.

        c)        green ppt. does not redissolve in excess sodium hydroxide solution

d)        sample solution: add ammonia solution Þ green ppt.

        e)        green ppt. redissolve in excess ammonia solution

f)        sample solution: add acidified potassium permanganate solution Þ turn brown Þ Fe²⁺ exists

        g)        sample solution: add dilute silver nitrate solution Þ yellow ppt.

        h)        yellow ppt. redissolve in concentrated ammonia solution Þ Br^- exists

6.     Iron(III) sulphite

a)        soluble in water and give a yellow / brown solution Þ some coloured ions exist

        b)        sample solution: add sodium hydroxide solution Þ brown ppt.

        c)        brown ppt. does not redissolve in excess sodium hydroxide solution

d)        sample solution: add ammonia solution Þ brown ppt.

        e)        brown ppt. redissolve in excess ammonia solution Þ Fe³⁺ exists

f)        add dilute hydrochloric acid on solid sample Þ colourless gas with choking smell

        g)        colourless gas turn lime water milky Þ SO₃^2- or CO₃^2-

h)        colourless gas turn the colour of Cr₂O₇^2-/H⁺ from orange to green Þ SO₃^2- exists

 

 

Suggested Answers on Note (Chapter 29) P.8 - 10

 

1.	D	6.	A	11.	A	16.	C	21.	B
2.	A	7.	A	12.	B	17.	D
3.	A	8.	C	13.	A	18.	D
4.	D	9.	B	14.	B	19.	C
5.	B	10.	C	15.	C	20.	C