Acids, Bases and Salts

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Acids in which complete dissociation of hydrogen ion takes place are called strong acid.

Acids produce H⁺ ions in presence of water.

H⁺ ions cannot exist alone, they exist as H₃O⁺ (hydronium ions).
H⁺ + H₂O → H₃O⁺
HCl + H₂O → H₃O+ + Cl⁻

While diluting acids, it is recommended that the acid should be added to water and not water to acid because the process of dissolving an acid or a base in water is highly exothermic.

Bases in which complete dissociation of hydroxide ion takes place are called strong base.

NaOH + H₂O → Na⁺  + OH-
Mg(OH) + H₂O → Mg²⁺ + 2OH^-

Bases soluble in water are called alkali.

pH stands for the power of hydrogen ion concentration in a solution. pH values decide whether a solution is acidic or basic or neutral.

mathematically expressed as
pH = -log10[H⁺]
For neutral solution [H⁺] = 10^–7M; pH = 7

For acidic solution [H⁺] > 10^–7M; pH < 7

For basic solution [H⁺] < 10^–7M; pH > 7

When OH^–

ions are taken into account the pH expression is replaced by pOH
pOH = -log10[OH^–]

The strength of acid or base depends upon the hydrogen ion concentration.

pH = 7 → neutral solution
pH less than 7 → acidic solution
pH more than 7 → basic solution

Acids in which complete dissociation of hydrogen ion takes place are called strong acid.

Acids produce H⁺ ions in presence of water.

H⁺ ions cannot exist alone, they exist as H₃O⁺ (hydronium ions).
H⁺ + H₂O → H₃O⁺
HCl + H₂O → H₃O+ + Cl⁻

While diluting acids, it is recommended that the acid should be added to water and not water to acid because the process of dissolving an acid or a base in water is highly exothermic.

Bases in which complete dissociation of hydroxide ion takes place are called strong base.

NaOH + H₂O → Na⁺  + OH-
Mg(OH) + H₂O → Mg²⁺ + 2OH^-

Bases soluble in water are called alkali.

pH stands for the power of hydrogen ion concentration in a solution. pH values decide whether a solution is acidic or basic or neutral.

mathematically expressed as
pH = -log10[H⁺]
For neutral solution [H⁺] = 10^–7M; pH = 7

For acidic solution [H⁺] > 10^–7M; pH < 7

For basic solution [H⁺] < 10^–7M; pH > 7

When OH^–

ions are taken into account the pH expression is replaced by pOH
pOH = -log10[OH^–]

The strength of acid or base depends upon the hydrogen ion concentration.

pH = 7 → neutral solution
pH less than 7 → acidic solution
pH more than 7 → basic solution

pH in the human body

1. Using pH factor the healthiness of our body is predicted. At pH level 6.9, the body becomes prone to viral infections like colds, cough and flu. Cancer cells thrive inside the body at a pH of 5.5.
2. The pH of a normal, healthy human skin is 4.5 to 6. Proper skin pH is essential for a healthy complexion.
3. pH of stomach fluid is approximately 2.0. This fluid is essential for the digestion of food.
4. Human blood pH range is 7.35 to 7.45. Any increase or decrease in this value leads to diseases. The ideal pH for blood is 7.4.
5. pH of normal saliva ranges between 6.5 to 7.5.
6. White enamel coating in our teeth is calcium phosphate, the hardest substance in our body. It does not dissolve in water. If pH of mouth falls below 5.5, the enamel gets corroded.

pH in soil

In agriculture, the pH of soil is very important. Citrus fruits require slightly alkaline soil, while rice requires acidic soil and sugar cane requires neutral soil.

pH in rainwater

pH of rainwater is approximately 7 showing a high level of its purity and neutrality. If rainwater is polluted by SO₂ and NO₂, acid rain occurs, bringing the pH value less than 7.