Increasing Order of pH of 0.1 M Solution of the Components:


The compound NH4Cl is formed by the reaction between ammonium ion (NH4+) and chloride ion (Cl-). In water, NH4Cl dissociates into NH4+ and Cl-. The ammonium ion is a weak acid that can donate a proton (H+) to the solution, resulting in the formation of NH3 (ammonia) and H3O+ (hydronium ion). The chloride ion, on the other hand, does not affect the pH of the solution. Therefore, NH4Cl will decrease the pH of the solution, making it acidic.


CH3COONa is the salt of acetic acid (CH3COOH) and sodium hydroxide (NaOH). When dissolved in water, CH3COONa dissociates into CH3COO- and Na+ ions. The acetate ion (CH3COO-) is the conjugate base of acetic acid and can accept a proton (H+) from the solution, resulting in the formation of acetic acid and OH- (hydroxide ion). This reaction will slightly increase the pH of the solution, making it slightly basic.


CH3COOHNH4 is the salt of acetic acid and ammonium hydroxide (NH4OH). Similar to CH3COONa, when dissolved in water, CH3COOHNH4 dissociates into CH3COO- and NH4+ ions. The acetate ion can accept a proton from the solution, resulting in the formation of acetic acid and OH- (hydroxide ion). However, the ammonium ion (NH4+) can donate a proton to the solution, resulting in the formation of NH3 and H3O+ (hydronium ion). The acidity of the ammonium ion is stronger than the basicity of the acetate ion, so the overall effect is slightly acidic.


HCOONH4 is the salt of formic acid (HCOOH) and ammonium hydroxide. When dissolved in water, HCOONH4 dissociates into HCOO- and NH4+ ions. The formate ion (HCOO-) can accept a proton from the solution, resulting in the formation of formic acid and OH- (hydroxide ion). Similar to CH3COOHNH4, the ammonium ion (NH4+) can donate a proton to the solution, resulting in the formation of NH3 and H3O+ (hydronium ion). The acidity of the ammonium ion is stronger than the basicity of the formate ion, so the overall effect is slightly acidic.

Increasing Order of pH:
Based on the explanations above, the correct increasing order of pH of the 0.1 M solutions is as follows:

1. NH4Cl (most acidic)
2. HCOONH4
3. CH3COOHNH4
4. CH3COONa (least acidic, slightly basic)

Therefore, the correct order