pH of Salts

Key Concepts

• pH of salts
• Acidic salts
• Basic salts
• Neutral salts

Introduction: 

pH in everyday life: 

pH is used for digestion. pH is used to crop plants in soil. pH is used as self-defence by plants and animals. pH knowledge helps prevent tooth decay, maintain the health of plants, etc.  

Explanation: 

Salts: 

Salts are substances usually formed by reacting an acid with a base. Salts are neutralized products. 

Salt formation: 

Salts are formed by exchanging ions between an acid and a base called a neutralization reaction. 

Example: HCl + NaOH → NaCl + H₂O 

The pH of salts: 

Salts have a wide range of pH; accordingly, their nature varies. 

1. Acidic salts 
2. Basic salts 
3. Neutral salts 

Acidic salts: 

Salts that have a pH of less than 7 are acidic salts. Acidic salts are formed from a strong acid and weak base. 

Example: HCl + NH₄OH →  NH₄Cl + H₂O 

Basic salts: 

Salts that have a pH greater than 7 are basic salts. Basic salts are formed from a strong base and weak acid.  

Example: CH₃COOH + NaOH → CH₃COONa + H₂O 

Neutral salts: 

Salts that have a pH equal to 7 are neutral salts. Neutral salts are formed from a strong base and strong acid. 

Example: HCl + NaOH → NaCl + H₂O 

Salts family:

Sodium salts 

Salts that contain sodium cation or positive radicals are considered sodium salts. 

Example: Sodium chloride and Sodium sulfate  

Chloride salts: 

Salts that contain chloride anion or negative radicals are considered chloride salts. 

Example: Sodium chloride and Potassium chloride 

Activity: 

Write the chemical formula for the following compounds: 

1. Sodium chloride  
2. Sodium sulfate 
3. Potassium chloride  
4. Potassium sulfate 
5. Aluminum chloride 

Identify from which acid and base they are obtained. Find the family of salts.  

Results: 

Sodium chloride & sodium sulfate belongs to the sodium family. Potassium chloride & potassium sulfate belongs to the potassium family. Sodium chloride & aluminum chloride belongs to the chloride family. 

Ionic salts and Covalent salts: 

Salts that can be dissolved in water completely and turn into ions are called ionic salts.  

Example: Magnesium carbonate, Sodium carbonate 

Salts that are partially dissolved or not dissolved in water are called covalent salts.  

Example: Glucose, Fructose 

Activity: 

Collect salts samples –

1. Sodium chloride 
2. Potassium nitrate 
3. Aluminum chloride 
4. Zinc sulfate 
5. Copper sulfate 
6. Sodium acetate 
7. Sodium carbonate 
8. Sodium hydrogen carbonate 

Check the solubility in distilled water. Find the pH of solutions with litmus paper. List them as acidic, basic and neutral salts. 

Observations: 

Salts that are soluble in water – 

1. Sodium chloride – sodium ion & chloride ion 
2. Potassium ion & nitrate ion 
3. Aluminum ion & chloride ion  
4. Zinc ion & sulfate ion  
5. Copper sulfate 
6. Sodium acetate 
7. Sodium carbonate 
8. Sodium hydrogen carbonate 

Results: 

Acidic salts (turns blue to red) –

1. Aluminum chloride 
2. Zinc sulfate  
3. Copper sulfate 

Basic salts (turns red to blue) –

1. Sodium acetate 
2. Sodium carbonate 
3. Sodium hydrogen carbonate  

Neutral salts (no change in litmus) – Sodium chloride 

Chemical formula and common names of salts: 

Salts are given a chemical formula based on the number of cations and anions present in the substance. 

Chemical names –

1. Sodium chloride – NaCl Sodium chloride – Table salt  
2. Potassium nitrate- KNO₃ – saltpeter 
3. Aluminum chloride-AlCl₃ 
4. Zinc sulfate-ZnSO₄ – White vitriol 
5. Copper sulfate-CuSO₄ -Blue vitriol 
6. Sodium acetate-CH₃COONa 
7. Potassium nitrate 
8. Sodium carbonate-Na₂CO₃-Washing soda 
9. Sodium hydrogen carbonate-NaHCO₃ – Baking soda  

Summary

• Salts have different pH values and according to they are three types-Acidic, basic and neutral.
• Salts pH can be identified by dissolving them in water and forming ions and testing with litmus paper.
• Acidic salts are formed from strong acid and weak base.
• Basic salts are formed from strong base and weak acid.
• Neutral salts are formed by strong acid and strong base.