Page 153 - Chemistry

–It is prepared by dissolving 20.8G of Iron (II) Sulphate in1litre of distilled water, add
a few drops of concentrated sulphuric (VI) acid, to avoid oxidation.
3. Solution X 3 contains 3.45g of sodium nitrite in 1 litre of solution
4. Solid M – Potassium nitrate
5. Solid Y - (Oxalic acid)
1. You have been provided with:
(i) Solution X 1, acidified Potassium manganate (VII) solution
(ii) Solution X 2, 0.1M FeSO 4
(iii) Solution X 3, Sodium Nitrite

You are required to:
(a) Standardize solution X 1, using X 2
(b) Use experimental results to write ionic equation for the reaction between manganate
(VII) ions and nitrate ions

Procedure I:-
(i) Fill the burette with solution X 1
3
(ii) Pipette 25cm of solution X 2 into 250ml conical flask
(iii) Titrate solution X 2 with solution X 1 until a pink colour just appear
(iv) Record your results in table 1:
TABLE 1
3
Final burette reading (cm ) I II III
3
Initial burette reading (cm )
3
Volume of X 1 used cm

Calculations:
(a) Calculate the average volume of solution X 1 used
3
2+
(b) Calculate the number of moles of Fe in 25cm of solution X 2 used
3
2+
(c) If the ratio MnO 4-: Fe is 1:5, calculate the concentration of MnO 4 ions in moles per dm
Procedure II:

(i) Rinse the conical flask and refill the burette with solution X 1
3
(ii) Pipette 25cm of X 3 into a clean conical flask
o
(iii) Warm this solution to about 50 C (Note: Be accurate with temperature)
(iv) Titrate the solution in (iii) above against solution X 1 from the burette to a pink colour
(v) Record your results in table II.

Calculations:
(a) Calculate the average volume of X 1 used
(b) Calculate the number of moles of :
(i) Sodium nitrite in one litre of solution (Na = 23, N = 14, O = 16)
3
(ii) Nitrite ions in 25cm of solution X 3 used
(iii) Moles of solution X 1 used
-
(c) (i) Work out the approximate ratio Mno 4-: NO 2
(ii) Write down the ionic equation for the reaction between acidified manganate
(VII) ions and nitrite ions
2. You are provided with solid M. You are required to:
(i) Carry out test on solid M
(ii) Record your observations and inferences accordingly.

Procedure:-

www.kcse-online.info 152