Select the correct increasing order of pH for 0.1 M solutions of the following substances:

Calculate the pOH of a solution at 25$°$C that contains 1x10^-10 M of hydronium ion.   

1. 7.00

2. 4.00

3. 9.00

4. 1.00

For a given solution pH = 6.9 at 60$°$C, where K_w=10^-12. The solution is:

1. acidic                                         

2. basic

3. neutral                                         

4. unpredictable

What happens to pH of a solution when NH₄Cl crystal is added to a dilute solution of NH₄OH?

1. Decreases                                   

2. Increases

3. Remains unaffected                       

4. All of the above

The phenomenon of interaction of anions and cations furnished by an electrolyte with the H⁺ and  OH^- ions of water to produce acidic nature or alkalinity is known as hydrolysis. 
Find the correct statement(s) regarding salt hydrolysis.

1. Salt hydrolysis may increase or decrease the pH of the solution.

2. All the salts (except those made up with strong acid and base) undergo hydrolysis

3. The variation of pH depends upon the nature of the salts as well as on the temperature

4. All of the above