Science
Methyl orange is added to dilute hydrochloric acid and to aqueous sodium hydroxide. What is the colour of the methyl orange in each solution?
| Sample | Colour in dilute hydrochloric acid | Colour in aqueous sodium hydroxide |
|---|---|---|
| A | Orange | Red |
| B | Red | Yellow |
| C | Red | Orange |
| D | Yellow | Red |
options
- A
- B
- C
- D
Answer
B
Reason — Methyl orange is an acid-base indicator that changes colour depending on the pH of the solution:
- In acidic solutions (like dilute hydrochloric acid), methyl orange turns red.
- In basic solutions (like aqueous sodium hydroxide), it turns yellow.
Hence, Methyl orange turns red when added to dilute hydrochloric acid and yellow when added to aqueous sodium hydroxide.
Related Questions
Four statements about the reactions of oxides with dilute hydrochloric acid and aqueous sodium hydroxide are listed.
I. Aluminium oxide reacts with both dilute hydrochloric acid and aqueous sodium hydroxide.
II. Calcium oxide reacts with dilute hydrochloric acid and aqueous sodium hydroxide.
III. Zinc oxide reacts with both dilute hydrochloric acid and aqueous sodium hydroxide.
IV. Sulphur dioxide does not react with either dilute hydrochloric acid or aqueous sodium hydroxide.
Which statements are correct?
options
- I and II
- I and III
- II and IV
- III and IV
An iron nail is added to each of the two test tubes ‘P’ and ‘Q’ containing aqueous copper (II) sulphate and aqueous silver nitrate respectively. Which of the following observation is correct?
options
- In test tube ‘P’ iron nail is coated with a blue coating and in test tube ‘Q’ there is no reaction.
- Iron nail is coated with a brown coating in test tube ‘P’ and silver coating in test tube ‘Q’.
- There is no reaction in either of the test tubes ‘P’ or ‘Q’.
- There is no reaction in test tube ‘P’ but a silver coating on iron nail is seen in test tube ‘Q’.
Which of the following substances when dissolved in equal volume of water, will have the highest pH value?
options
- Sulphuric acid
- Acetic acid
- Magnesium hydroxide
- Sodium hydroxide
When excess of carbon dioxide is passed through lime water, the milkiness disappears because
options
- Water soluble calcium carbonate converts to water soluble calcium bicarbonate.
- Insoluble calcium carbonate converts to water soluble calcium bicarbonate.
- Water soluble calcium carbonate converts to insoluble calcium bicarbonate.
- Insoluble calcium carbonate converts to insoluble calcium bicarbonate.