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 inorganic 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. Stir, filter, and keep the filtrate and the residue.
(b) Put the residue into a test tube and add about 5 cm\(^3\) of dilute HCl. Shake to dissolve
(i) To about 2 cm\(^3\) of the solution, add NaOH\(_{(aq)}\) in drops and then in excess
(ii) To another 2 cm\(^3\) portion of the solution, add NH\(_{3(aq)}\) in drops and then in excess.
(c) To about 2 cm\(^3\) portion of the filtrate, add few drops of dilute HNO\(_3\), and then AgNO\(_{3(aq)}\) a followed by aqueous NH\(_3\) in excess.
Explanation
| test | Observation | Inference |
| (a) C + water and filter | White residue partially dissolved | |
|
(b) Residue + dil. HCl + shake |
Effervescence occur, Colorless gas evolved. Gas turns lime water milky |
Gas is co\(_2^-\) CO\(_3^{2-}\) or HCO\(_3\) present |
|
(i) Solution in (b) + NaOH in drops Then in excess |
White gelatinous ppt. ppt soluble in excess NaOH |
Zn\(^{2+}\), Al\(^{3+}\) or Pb\(^{2+}\) present |
|
(ii) Solution in (b) + NH\(_3\) solution in drops then in excess |
White gelatinous ppt.ppt soluble in excess NH\(_{3(aq)}\) |
Zn\(^{2+}\) confirmed |
|
(c) Filtrate + dil. HNO\(_3\) + AgNO\(_{3(aq)}\) + NH\(_3\) solution in excess |
No visible reaction White ppt formed. ppt dissolved in excess NH\(_{3(aq)}\) |
Cl\(^{-}\) present Cl\(^{-}\) confirmed |