Credit will be given for strict adherence to the instructions, for observations precisely recorded, and for accurate inferences. AIl tests. observations and inferences must be clearly entered in your answer book, in ink, at the time they are made.
C is a double salt. Carry out the following exercises on C. Record your observations and identify any gas(es) evolved. State the conclusion drawn from the result of each test.
a) Put all of C into a test tube. Add about 5cm\(^3\) of distilled water, stir and test with litmus paper. Divide the Solution into two portions
(b) To the first portion, add sodium hydroxide solution in drops and then in excess. Heat the resulting mixture and keep it for minutes.
(c) To the second portion, add few drops of Bacl\(_{2(aq)}\) followed by excess dilute hydrochloric acid
Explanation
| TEST | OBSERVATION | INFERENCE |
| (a) C\(_{(s)}\) + H\(_2\)O |
C dissolved to form a light green solution The solution turned blue litmus paper red |
C is a soluble salt Solution is acidic |
|
(b) C\(_{(aq)}\) + NaOH\(_{aq}\) in drop-wise In excess then heat
Keeping for some minutes
|
Green precipitate formed Precipitate insoluble in excess A choking/pungent/irritating (colourless) gas evolved which turns litmus paper blue/forms dense white fumes with conc.HCl
The precipitate turned brown (at the upper part of the tube)
|
Fe\(^{2+}\) present
NH\(_3\) gas from NH\(_4^+\)
Fe\(^{2+}\) oxidized to Fe\(^{3+}\) |
| (c) C\(_{(aq)}\) + BaCl\(_{2(aq)}\) + HCl\(_{(aq)}\) |
White precipitate formed Precipitate undissolved |
SO\(_4^{2-}\) or SO\(_3^{2-}\) or CO\(_3^{2-}\) SO\(_4^{2-}\) |