Credit will be given for strict adherence to instructions, for observations precisely recorded, and for accurate interference. All tests, Observations and inferences must be clearly entered in your answer book, in ink at the time they are made. C and D are aqueous solutions of simple salt and an inorganic compound respectively. Carry out the following exercises on C and D. Record your observations and identify the gasses evolved. State the conclusion and draw from the result in the test and add sodium hydroxide in excess.
(b)(i) Test D with litmus paper
(ii) Put about 5cm\(^3\) of D in a test tube and add sodium hydroxide solution in drops and then in excess
(iii) Add about 1cm\(^3\) of the soap solution provided to about 10 cm\(^3\) of D mixture. Repeat the test using distilled water in place D
Explanation
| (a) Test | Observation | Inference |
| (i) C + NaOH\(_{(aq)}\) + heat |
Colourless gas with choking/smell Gas produced dense white fumes with concentrated HCI Gas turned red litmus paper blue |
Gas is NH\(_3\) from NH\(_4\) |
| (ii) C + BaCl\(_2\) + dil. HCl in excess |
White precipitate Precipitate remained Precipitate insoluble in dilute HCl |
SO\(_4^{2-}\) or CO\(_3^{2-}\) or SO\(_3^{2-}\) SO\(_4^{2-}\) present |
| (b)(i) D + litmus paper | Red litmus turned blue | D is alkaline |
| (ii) D + NaOH\(_{(aq)}\) in drops; then in excess |
White precipitate Precipitate insoluble in excess |
Ca\(^{2+}\) present or mg\(^{2+}\) present |
|
(iii) D shaken with soap solution with soap solution Distilled water shaken with the soap solution |
No lather formation/scum was formed with D Lather formed easily with distilled water |
Hardness in D due to pressure of Ca\(^{2+}\)/mg\(^{2+}\) |