Question

Identify an unknown solution (1, 2, 3 and 4) and fill the vacancies in the table

Procedure

The unknown solutions are : HCl, NaOH,   Acetic acid, Na₂CO₃

1. Test each solution with litmus paper. Record the results in the data table below.
2. Take little of each solution in a test tube and add 5 drops of silver nitrate to each solution. Record the results in the data table.
3. Take little of each solution in a test tube and add two drops of phenolphthalein methyl orange to each solution. Record the results in the data table.
4. Take little of each solution in a test tube and add one drop of methyl orange to each solution. Record the results in the data table.

Observations:

Unknown solution No.		1	2	3	4
Litmus test	Red	Red	Blue	Blue	Red
	Blue	Red	Blue	Blue	Red
Silver nitrate (AgNO3) Test		No ppt.	White/yellow ppt.	Brown ppt.	White ppt.
Phenolphthalein test
Methyl Orange Test
Identity of Solution

Identify an unknown solution (1, 2, 3 and 4) and fill the vacancies in the table Procedure The unknown solutions are : HCI, NaOH, Acetic acid, Na2CO3 1- Test each solution with litmus paper. Record the results in the data table below. 2- Take little of each solution in a test tube and add 5 drops of silver nitrate to each solution. Record the results in the data table. 3- Take little of each solution in a test tube and add two drops of phenolphthalein methyl orange to each solution. Record the results in the data table. 4- Take little of each solution in a test tube and add one drop of methyl orange to each solution. Record the results in the data table. Observations: 2 T 4 Unknown solution No. Red Red Blue Blue Red Litmus test Blue Red Blue Blue Red Silver nitrate (AgNO3) Test White/yellow ppt. Brown ppt. No ppt. White ppt. Phenolphthalein test Methyl Orange Test Identity of Solution

Answer 1

Ans: Indentification of unknwns are as follows:

Unknown # 1 = Red litmus no color change = an acid

                        = Blue litmus turns to Red = an acid

                        = No ppt with AgNO3 = could be Acetic acid as silver acetate does not give ppt.

                        = Phenolphthalein= No Colour (an acid)

                        = Methyl orange = Pink - Red color (in acid)

                        = It is Acetic acid from the above observations and the choices given

Unknown # 2   = Red litmus to Blue = a base

                        = Blue litmus = no change in color = a base

                        = White yellow ppt with AgNO3 = Silver carbonate is a yellow white ppt = Phenolphthalein = Pink - Red Colour (a base)

                        = Methyl orange = Yellow color (a base)

                        = It is Sodium carbonate (Na2CO3) acid from the above observation

Unknown # 3 = Red litmus to Blue = a base

                        = Blue litmus = no change in color = a base

                        = Brown ppt with AgNO3 = brown ppt is of silver oxide by reaction with NaOH

                        = Phenolphthalein = Pink – Red Colour (a base)

                        = Methyl orange = Yellow color (a base)

                        = It is Sodium hydroxide (NaOH) from the above observation

Unknown # 4 = Red litmus no color change = an acid

                        = Blue litmus turns to Red = an acid

                        = White ppt with AgNO3 = AgCl is a white ppt by reaction with HCl

                        = Phenolphthalein= No Colour (an acid)

                        = Methyl orange = Pink - Red color (in acid)

                        = It is HCl from the above observations and the choices given