ALTERNATIVE TO PRACTICAL A

A  is a solution of KMnO\(_4\) containing 0.020 moldm\(^{-3}\). B is a solution of Fe\(^{2+}\) obtained by dissolving 3.8 g of iron granules in 250 cm\(^3\) of solution.

(a)Put A in the burette. Pipette 20.0 cm\(^3\) or 25 cm\(^3\) of B into a conical flask and add 10 cm\(^3\) of H\(_2\)SO\(_4\). Titrate it with A.

     Repeat the titration to obtain concordant titre values. Tabulate your result and calculate the average volume of A used. 

     MnO\(_4\)\(^-\)\(_{(aq)}\) +  5Fe\(^{2+}\)\(_{(aq)}\)  +  8H\(^+\)\(_{(aq)}\) → Mn\(^{2+}\)\(_{(aq)}\)  + Fe\(^{3+}\)\(_{(aq)}\) +  4H\(_2\)O\(_{(l)}\)                 

[ KMnO\(_4\) = 158.0, Fe = 56.0 ]

(b) From your results and information provided, calculate the:

(i) concentration of B in moldm\(^{-3}\)

(ii)concentration of B in gdm\(^{-3}\)

(iii) mass of Fe\(^{2+}\) in 250 cm\(^3\) of B.

(iv) percentage of Fe\(^{2+}\) in the granules.

C is a mixture of two simple inorganic salts, one of which is a sodium salt.

Perform the following exercises on C. Record your observation and identify any gas(es) evolved. State the conclusions you draw from the results of each test.

(a) Put all of C into a test tube and add about 10 cm\(^3\) of distilled water and shake.

b(i) Put about 2 cm\(^3\) of the filtrate into a boiling tube and heat strongly.

  (ii) Put half of the residue into a test tube and add dil. HCl.

  (iii) To about 2 cm\(^3\) of the clear solution from b(ii), add aqueous NaOH in drops, then in excess.

  (iv) To another 2 cm\(^3\) of the clear solution from b(ii), add aqueous ammonia in drops, then in excess.

(a) Mention two gases that are soluble in water.

(b) Name two apparatus that could be used to measure 9.50 cm\(^3\) of a solution accurately.

(c) What is the use of a fume cupboard in the laboratory?

(d) Name three personal protective equipment that are used in the laboratory.

                 ALTERNATIVE PRACTICAL  B

D contains 6.30 g of HNO\(_3\) in 500 cm\(_3\) of solution. E was prepared by dissolving 8.20 g of washing soda crystals ( Na\(_2\)CO\(_3\).xH\(_2\)O) in 250 cm\(^3\) of distilled water.

(a) Put D into the burette and titrate it against 20.0 or 25.0 cm\(^3\) portion of E using methyl orange as indicator. 

     Repeat the exercise to obtain concordance titre values.

     Tabulate your results and calculate the average volume of the acid used.

(b) Write a balanced chemical equation for the reaction.

(c) From your results and the information given;

(i) calculate the concentration of E in moldm\(^{-3}\);

(ii) what is the value of x in Na\(_2\)CO\(_3\).xH\(_2\)O? [H= 1.0; C =12.0; O = 16.0; Na = 23.0; N = 14.0 ]

F is an inorganic salt. Carry out the following exercises on F. Record your observations and identify any gas(es) evolved. State the conclusions you draw from the results of each test.

(a) Transfer F into a test tube and add dil. HCl to it until a clear solution is obtained.

(b) Divide the clear solution obtained from (a) into two portions

(i) To the first portion add  NaOH\(_{(aq)}\) in drops and then in excess.

(ii) To the second portion, add few drops of potassium hexacyanoferrate (II) solution.