Credit will be given for strict adherence to instructions, for observations precisely recorded, and for accurate inferences. All tests, observations, and inferences must be clearly entered in your answer book, In ink, a the time they are made.
C is a mixture of two simple salts. Carry out the following exercises on C. Record your observations and identify any gases evolved. State the conclusion you draw from the result of each test.
(a) Add about 10cm\(^3\) of distilled water to all of C in a boiling tube. Shake the mixture and filter: Keep both the filtrate and the residue.
(b) Divide the filtrate into two portions.
(i) To the first portion, add about 2cm\(^3\) of barium chloride solution, followed by dilute hydrochloric acid in excess. Warm the mixture and identify any gas evolved.
(ii) To the second portion, add few drops of acidified potassium tetraoxomanganate (VIl) solution and shake.
(C) Put the residue in a test tube and add about 3cm\(^3\) of dilute hydrochloric acid Warm gently and identify any gas evolved. Keep the mixture.
(d) Divide the clear solution from (c) above into two portions
(i) To the first portion, add sodium hydroxide solution in drops and then in excess.
(ii) To the second, add aqueous ammonia in drops and then in excess.
Explanation
C is a mixture of Na\(_2\)SO\(_3\) and CuCO\(_3\)
| Test | Observation | I Inference |
| (a) C + water; filtered |
Colourless filtrate or solution Green residue |
|
| (b)(i) Filtrate form (a) + BaCl\(_{2(aq)}\) + Hcl and warm |
White precipitate Effervescence gas evolved which is colourless which is colourless with pungent choking or sharp irritating smell which decolourise KMnO\(_4\). The ppt. dissolved The gas can also decolourise K\(_2\)Cr\(_2\)O\(_7\) |
CO\(^{2-}_3\) or SO\(_3^{2-}\) or SO\(_4^{2-}\) or S\(^{2-}\) Gas is SO\(_2\) from SO\(_3^2\) |
| (ii) Filtrate from (a) + KMnO\(_{4(aq)}\) | KMnO\(_4\), decolourised or the purple colour discharged | Reducing agent present |
| (c) Residue + dil. HCl + heat | Gas evolved, effervescence colourless, odourless turns lime water milky blue/green solution | Gas is CO\(_2\) from CO\(_3^{2-}\)/HCO\(_3\) |
| (d)(i) Solution from (c) + NaOH\(_{(aq)}\) in drops then in excess |
Blue ppt. ppt. remained insoluble |
Cu\(^{2+}\) present
|
| (ii) Solution from (c) + NH\(_{3(aq)}\) in drops, then in excess |
pale blue ppt. ppt. dissolved to give a deep bless solution |
CU\(^{2+}\) |