Acids Bases And Salts Test - 2

pH is a numeric scale used to specify the acidity or basicity of an aqueous solution. Solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic. With a pH value of 5, coffee is acidic in nature.

Urine pH is used to classify urine as either a dilute acid or base solution. Seven is the point of neutrality on the pH scale. The lower the pH, the greater the acidity of a solution; the higher the pH, the greater the alkalinity. The glomerular filtrate of blood is usually acidified by the kidneys from a pH of approximately 7.4 to a pH of about 6 in the urine. Depending on the person\'s acid-base status, the pH of urine may range from 4.5 to 8.

For bases, the value of pH is greater than 7, i.e. the stronger the base, the higher the pH value. Out of the given options, HCl and CH₃COOH are acids whose pH value is less than 7 and out of Ca(OH)₂ and NaOH, NaOH is the stronger base. Thus, NaOH has the highest pH value among these all.

Rain is considered to be the purest form of water, but the gaseous oxides of carbon, sulphur and nitrogen dissolve in the rain water to form acids which come down with rain. Normally, rain has a pH value between 5.0 and 5.5, which is slightly acidic. However, when the pH of rain water drops below 5.6, it is referred to as acid rain. Typical acid rain has a pH value of 4.0.

Phenolphthalein solution is colourless and shows no colour change when added to acidic solutions.

However, it gives a pink colour with basic solutions.

K₂SO₄ does not undergo hydrolysis.

Potassium sulphate is salt of strong acid and strong base. Such salts do not undergo hydrolysis when dissolved in water and their solutions are neutral. In this case, neither the cations nor the anions undergo hydrolysis.

A salt is a product of the reaction of an acid with a base. NH₄NO₃ is formed by the reaction of a weak base and a strong acid. The chemical equation for the hydrolysis of NH₄NO₃ can be written as:

NH₄NO₃ + H₂O → NH₄OH + H⁺(aq) + NO₃^-(aq)

NH₄OH is written in the unionised state because it is a weak electrolyte and a weak base while HNO₃ is a strong acid.

(NH₄)₂CO₃ is a salt of a weak acid and a weak base. The hydrolysis reaction is:

(NH₄)₂CO₃ + 2H₂O → 2NH₄OH + H₂CO₃

Both NH₄OH and H₂CO₃ are written as unionised compounds because they are classified as weak base and weak acid, respectively.

The pH scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic. If the pH of a solution is zero, then the solution is highly acidic.