Question

The following observations were made when different indicators were added to three unknown solutions A, B and C. Choose the option depicting correct set of compounds A, B and C.

Compound	Phenolphthalein	Methyl Orange
A	Methyl Orange	No change
B	Pink	Yellow
C	No change	Red

• A. A: NaOH ; B: HCl ; C: $C_6{H}_{12}{O}_6$
• B. A: HCl ; B: $C_6{H}_{12}{O}_6$ ; C: NaOH
• C. A: HCl ; B: NaOH ; C: $C_6{H}_{12}{O}_6$
• D. A: $C_6{H}_{12}{O}_6$ ; B: NaOH ; C: HCl

Answer 1

The correct option is D A: $C_6{H}_{12}{O}_6$ ; B: NaOH ; C: HCl

• Substance A shows no visible colour change with phenolphthalein, thus it can be inferred that it is acidic or neutral.
• Since it shows no change with the methyl orange indicator too, it is neutral in nature.
• Substance B turns pink when added to the phenolphthalein indicator, thus it can be inferred that it is basic in nature.
• Since it turns the methyl orange indicator yellow, it can be concluded that it is a base.
• Substance C shows no visible colour change with phenolphthalein, thus it can be inferred that it is acidic or neutral.
• Since it turns the methyl orange indicator red, it can be confirmed that it is acidic in nature.
• Therefore, the correct answer is option C.