Science
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
Answer
Sodium hydroxide
Reason — The pH value of a solution indicates how acidic or basic it is :
- Acids have low pH values (< 7).
- Bases (alkalis) have high pH values (> 7).
Now,
- Sulphuric acid (H2SO4) is a strong acid, so it has a very low pH.
- Acetic acid (CH3COOH) is a weak acid, so its pH is slightly higher than that of sulphuric acid but still below 7.
- Magnesium hydroxide (Mg(OH)2) is a slightly soluble weak base, so it has a moderately high pH, but not the highest.
- Sodium hydroxide (NaOH) is a strong base, completely dissociates in water to produce a large amount of OH- ions, giving it the highest pH value (around 14).
Hence, when equal volumes of these substances are dissolved in water, sodium hydroxide will have the highest pH value.
Related Questions
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’.
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
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.
In the reaction of aqueous solution of barium chloride with aqueous solution of sodium sulphate, the aqueous solution formed will be:
options
- BaCl2
- BaSO4
- Na2SO4
- NaCl