NTA Abhyas 2020
- Exam
- NTA Abhyas
- Year
- 2020
- Subject
- Chemistry
- Chapter
- Redox Reactions
NTA Abhyas 2020 · Chemistry · Redox Reactions
An alkali is titrated against an acid with methyl orange as...
An alkali is titrated against an acid with methyl orange as indicator, which of the following is a correct combination?
Options
- A
Base Acid End point Strong Strong Pink to colourless - B
Base Acid End point Weak Strong Colourless to pink - C
Base Acid End point Strong Strong Pinkish red to yellow - D
Base Acid End point Weak Strong Yellow to pinkish red
Correct answer
D.
| Base | Acid | End point |
| Weak | Strong | Yellow to pinkish red |
Step-by-step solution
Methyl orange is weak organic base. It is used in the titration of weak base vs strong acid.
\mathop{MeOH}_{\mathop{\text{Unionized form}_{( \text{Yellow} )}} ⇌ Me^{+} + \mathop{OH^{-}}_{\mathop{\text{Ionized form}_{( \text{Red} )}}
In basic medium, equilibrium lies in backward direction and therefore it shows yellow colour.
In acidic medium, equilibrium shifts in forward direction and therefore, colour changes from yellow to red.
\mathop{MeOH}_{\mathop{\text{Unionized form}_{( \text{Yellow} )}} ⇌ Me^{+} + \mathop{OH^{-}}_{\mathop{\text{Ionized form}_{( \text{Red} )}}
In basic medium, equilibrium lies in backward direction and therefore it shows yellow colour.
In acidic medium, equilibrium shifts in forward direction and therefore, colour changes from yellow to red.