CBSE
Class 10
Class 12
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
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.