While preparing soap a small quantity of common salt is generally added to the reaction mixture of vegetable oil and sodium hydroxide. Which one of the following may be the purpose of adding common salt?
To reduce the basic nature of the soap
To make the soap neutral
To enhance the cleansing power of the soap
To favour the precipitation of the soap
(4)
A small quantity of common salt is generally added to the reaction mixture of vegetable oil and sodium hydroxide to favour the precipitation of the soap because by adding salt to the suspension mixture, soap is precipitated as solid. This process is called salting out of soap
When a small amount of acid is added to water, the phenomena which occur are
(A) Dilution
(B) Neutralisation
(C) Formation of ions
(D) Salt formation
The correct statements are :
(A) and (C)
(B) and (D)
(A) and (B)
(C) and (D)
(1)
When a small amount of acid is added to water, the phenomena which occur are dilution and formation of ions. When water is added, a concentrated acid is turned into a dilute acid. This process is called dilution of acid. A dilute acid is an aqueous solution in which acid undergoes ionisation and releases hydronium ions
If a few drops of a concentrated acid accidentally spills over the hand of a student, what should be done?
Wash the hand with saline solution.
Wash the hand immediately with plenty of water and apply a paste of sodium hydrogen carbonate.
After washing with plenty of water apply solution of sodium hydroxide on the hand.
Neutralise the acid with a strong alkali.
(2)
If a few drops of a concentrated acid accidentally spills over the hand of a student then he should wash his hands immediately with plenty of water as it will dilute the acid and wash it out. Any remaining acid should be neutralised by applying the paste of sodium hydrogen carbonate.
Which one of the following types of medicines is used for treating indigestion?
Antibiotic
Analgesic
Antacid
Antiseptic
(3)
Antacids such as sodium bicarbonate and magnesium hydroxide etc. are used in treating indigestion. They are basic in nature and react with excess acid present in the stomach and neutralise it.
Which of the following is used for dissolution of gold?
Hydrochloric acid
Sulphuric acid
Nitric acid
Aqua regia
(4)
Aqua regia is a mixture of hydrochloric acid and nitric acid in the ratio 3:1 and it can dissolve noble metals such as gold, palladium, and platinum, which however, are not soluble in either of the acids alone.
During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride is to:
Absorb the evolved gas
Moisten the gas
Absorb moisture from the gas
Absorb ions from the evolved gas
(3)
Calcium chloride is a drying agent used in the guard tube to absorb the moisture present in the air during hydrogen chloride gas preparation. Moisture must be removed to prevent the gas from forming white fumes, which occurs due to its reaction with water.
In an attempt to demonstrate electrical conductivity through an electrolyte, the following apparatus was set up. Which among the following statement(s) is(are) correct?
(a) Bulb will not glow because electrolyte is not acidic.
(b) Bulb will glow because NaOH is a strong base and furnishes ions for conduction.
(c) Bulb will not glow because circuit is incomplete.
(d) Bulb will not glow because it depends upon the type of electrolytic solution.
(i) and (iii)
(ii) and (iv)
(ii) only
(iv) only
(2)
Bulb will glow because NaOH is a strong base that dissociates completely in water into ions and ions which are responsible for electrical conductivity.
10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralise it will be:
4 mL
8 mL
12 mL
16 mL
(4)
Given: 10 mL of NaOH requires 8 mL of HCl.
Let X be the amount of HCl required to neutralise the 20 mL of NaOH.
20 mL of NaOH require = X HCl
X = (20 × 8) / 10
X = 16 mL
Generally metals react with acids to give salt and hydrogen gas. Which of the following acids does not give hydrogen gas on reacting with metals (except Mn and Mg)?
HCl
All of these
(3)
Nitric acid does not give hydrogen gas on reacting with metals (except Mg and Mn) because it is a strong oxidising agent and oxidises the evolved H? gas to water and itself gets reduced to the oxides of nitrogen. Whereas metals such as magnesium and manganese react with very dilute to evolve gas.
Which of these graphs shows how the pH of milk changes as it forms curd?
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(1)
Fresh milk has an acidic character due to its pH of 6.4 to 6.8. By the action of bacteria, this milk is transformed into curd, which further increases the curd's acidity and lowers its pH from 6 to less than 6.
