(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.
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 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
