(a) (i) What is meant by hardness of water?
(ii) Describe briefly how you would determine what proportion of hardness in a given sample of water is due to permanent hardness.
(iii) Give two reasons why hardness of water is an undesirable property.
(b) State the:
(i) reagents;
(ii) conditions for the laboratory preparation of trioxonitrate (V) acid.
(iii) How does concentrated trioxonitrate (V) acid reacts with:
(I) sulphur;
(II) aluminium.
(c) Name one amphoteric oxide.
(a) (i) When water does not easily form lather with soap / when water contains dissolved calcium and magnesium salts.
Water that does not easily lather with soap / Water that contains dissolved calcium and magnesium salts
(ii) Prepare soap solution
Measure volume of sample water from a burette or pipette titrate with shaking to permanent lather.
take titre value say x cm\(^3\)
Measure same volume of boiled sample water and then titrate with shaking take titre value say y cm\(^3\)
Find ratio; \(\frac{\text{permanent}}{\text{Total}}\) = \(\frac{y}{x}\)
(iii) Waste of soap
- produces scum during washing with soap
- blockage of pipes
- scales in boilers / furring of kettles
- leads to wastage of fuel
- not suitable for tanning / laundry / textile/ paper manufacturing industries
(b) (i) NaNO\(_3\) or KNO\(_3\)
conc H\(_2\)SO\(_4\)
(ii) concentrated H\(_2\)SO\(_4\)
heat (over a sand bath)
all glass apparatus
(iii) 2HNO\(_3\) + S → H\(_2\)SO\(_4\) + 2NO
OR
6HNO\(_3\) + S → H\(_2\)SO\(_4\) + 6NO\(_2\) + 2H\(_2\)O
II. no reaction / reaction prevented / metal passive oxide formed which coats metal
(c) Zinc oxide
Lead (II) oxide
Aluminium oxide
Tin(IV)oxide
Aluminium hydroxide
Tin (II) oxide
Lead (IV) oxide
Beryllium oxide
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