Credit will be given for strict adherence to the instructions, for observations precisely recorded and for accurate inferences. All tests, observations and inferences must be clearly entered in your answer book in ink, at the time they are made.
C is a mixture of two salts. Carry out the following exercises on C. Record your observations and identify any gas(es) evolved. State the conclusion you draw from the result of each test.
(a) Put all of C in a test tube and add about 10 cm\(^3\) of distilled water. Shake thoroughly and filter. Keep both the filtrate and the residue. Divide the filtrate into three portions.
(i) To the first portion, add NaOH\(_{(ag)}\) in drops and then in excess.
(ii) To the second portion, add NH\(_3\), solution in drops and then in excess.
(iii) To the third portion, add BaCl\(_{2(aq)}\) followed by dilute HCI.
(b) Divide the residue into two portions.
(i) Heat the first portion strongly in a test tube.
(ii) Add dilute HCI to the second portion.
Explanation
| Tes | Observation | Inference |
|
(a)(i) C + H\(_2\)O, then filter
(ii) Filterate + NaOH\(_{(aq)}\) in drops, then in excess
(iii) Filterate + NH\(_{3(aq)}\) in drops, then in excess
(iv) Filterate + BaCl\(_{2(aq)}\) + dil. HCl
(b)(i) First portion of residue + heat
(i) Second portion of residue + dil. HCl |
Green residue, blue filterate
Blue gelatinous precipitate insoluble in excess
Pale blue (gelatinous) precipitate ppt dissolves/soluble in excess to give a deep blue solution
White precipitate insoluble in dil. HCl
Colour changed from green to black powder
Effervescence, colourless, odourless gas which turned lime water milky
|
C is a mixture of soluble and insoluble salts
Cu\(^{2+}\) present
Cu\(^{2+}\) confirmed
SO\(_4^{2-}\) confirmed
Gas is CO\(_2\) from CO\(_3^2\) |