Railway Science (Chemistry-Acid ,Bases and Salt)

Milk of Magnesia {Magnesium hydroxide(Mg(OH)₂)} - It is a white solid and one of the key components of antacids. It is an alkaline solution of Water and Magnesium hydroxide. pH value of some common substances - Tomato juice - 4.7,Baking Soda - 8.3, Ammonia - 11, Vinegar - 2.8, Milk - 6.8, Pure water - 7.0, Rainwater - 6.5.

Acid + Base → Salt + Water. The reaction is - CH₃COOH (acetic acid) + NaOH (Sodium Hydroxide) → CH₃COONa (Sodium acetate) + H₂O (water). It is a neutralization reaction as an acid is reacting with a base to form salt and water. Sodium acetate could be used as additives in food, industry, concrete manufacture and in buffer solutions.

Copper hydroxide (Cu(OH)₂) is actually hydrated copper oxide, and it does provide some concentration of OH⁻ ions when it is in the presence of acids (H₃O⁺). However, it is largely insoluble in water.
Therefore, copper hydroxide would not be considered an alkali, but rather a weak base. An alkali is a basic hydroxide that produces negatively charged hydroxyl ions (OH⁻ ) when dissolved in water. Examples of Alkali: Sodium hydroxide (NaOH), Potassium hydroxide (KOH), etc.

Lime is added in the soil as lime is alkaline and it will neutralize the acidity of the soil and make it more neutral. It changes the pH of soil to less acidic. If the soil is too basic, acidic substances should be added to neutralize the pH of the soil. Compost is used in soil to improve the structure and health of soil by adding organic matter.

Sodium carbonate decahydrate (Na₂CO₃ ·10H₂O), also known as washing soda, is the most common hydrate of sodium carbonate containing 10 molecules of water of crystallization. Soda ash is dissolved in water and crystallized to get washing soda. It is white crystalline solid and is one of the few metal carbonates which are soluble in water. It is alkaline as the pH value of its solution is higher than 7. It has detergent properties through the process of saponification which makes fats and grease water-miscible. It is used in the manufacture of glass, soap and paper.

pH stands for 'potential of Hydrogen' which measures the acidity or alkalinity of aqueous solution developed in 1909 by Sorenson. The pH of a solution varies from 0 to 14. Solutions having a value of pH ranging from 0 to 7 are termed as acidic and the value of pH ranging from 7 to 14 are known as basic solutions. pH equal to 7 are known as neutral solutions. pH of some solutions Conic HCl (0), Saliva before meal (7.4), Toothpaste (8.0), Gastric Juice (1.4), Blood (7.4), Lemon Juice (2.5), Vinegar (4.0).

pH scale - used to measure acidic and basic nature of a solution, range - 0 to 14.

(synthetic indicator). Natural indicators - Indicators prepared from natural substances. example - turmeric, china rose, lichens, beetroot, etc. Synthetic indicators - indicators prepared from artificial substances and chemicals. Example - phenolphthalein, methyl red, etc.

Alkaline ions that directly neutralize the gastric acids of the stomach. Examples - Sodium Bicarbonate, aluminum hydroxide, aluminum phosphate and magnesium hydroxide etc. Effect of acidity - antacid with calcium may cause kidney stones.

Acid-Base Properties of Salts - Salts, when placed in water, will often react with the water to produce H₃O⁺ or OH⁻ i.e. hydrolysis reaction. Salts that are from strong bases and strong acids do not hydrolyze. Salts that are from strong bases and weak acids do hydrolyze, which gives it a pH greater than 7.
Salts of weak bases and strong acids do hydrolyze, which gives it a pH less than 7. pH (Power of Hydrogen) is a scale (0 - 14) used to specify the acidity or basicity of an aqueous solution. Lower pH values represent more acidic in nature, While higher pH values represent more basic or alkaline.