(a) (i) What is meant by hardness of water? (ii) Describe briefly how you would...
(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) Nameone amphoteric oxide.
Explanation
(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 titratewith shaking to permanent lather.
take titre value sayx 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