Question

Q. 7 (a) A solution has a pH of 7. Explain how you would you :
(i) increase its pH
(ii) decrease its pH
(b) If a solution changes the colour of the litmus from red to blue, what can you say about its pH ?
(c) What can you say about the pH of a solution that liberates carbon dioxide from sodium carbonate ?

Answer 1

Explanation:

7. a) i)Increase in pH can be done by adding a basic solution to it because increase in pH indicates a more basic medium. So, it needs to be more basic so a basic solution needs to added.

  ii)Decrease in pH can be done by adding an acidic solution because adding an acidic solution would lower the pH as lower the pH, the more acidic is the solution. So, adding an acidic solution would help lowering the pH

b) The pH is greater than 7 since, a basic solution turns litmus from red to blue. pH more than 7 refers to basic solution.

c) An acid reacts with sodium carbonate to release the carbon dioxide gas. So, pH less than 7 indicates acidic solutions and hence, the pH should be less than 7