English Medium Class 10 - CBSE Important Questions

Consider the following comments about saponification reactions:

I. Heat is evolved in these reactions.

II. For quick precipitation of soap, sodium chloride is added to the reaction mixtures.

III. Saponification reactions are a special kind of neutralisation reactions.

IV. Soaps are basic salts of long-chain fatty acids.

The correct comments are

(a) I, II and III

(b) II, III and IV

(c) I, II and IV

(d) Only I and IV

What do you observe when you drop a few drops of acetic acid to test tubes containing

(a) phenolphthalein

(b) distilled water

(c) universal indicator

(d) sodium hydrogen carbonate powder

Explain why carbon forms compounds mainly by covalent bond.

A student adds 2 mL of acetic acid to a test tube containing 2 mL of distilled water. He then shakes the test tube well and leaves it to settle for some time. After about 5 minutes he observes that in the test tube there is :

(A) a clear transparent colourless solution

(B) a clear transparent pink solution

(C) a precipitate settling at the bottom of the test tube

(D) a layer of water the layer of acetic acid

State the reason to explain why covalent compounds "have low melting and boiling points."

When you add about 2 ml of acetic acid to a test tube containing an equal amount of distilled water and leave the test tube to settle after shaking its contents, what will you observe in the test tube after about 5 minutes?

(A) A white precipitate settling at its bottom

(B) A clear colourless solution

(C) A layer of water over the layer of acetic acid

(D) A layer of acetic acid over the layer of water

A student adds a few drops of ethanoic acid to test tubes X, Y and Z containing aqueous solutions of sodium chloride, sodium hydroxide and sodium carbonate, respectively. If he now brings a burning splinter near the mouth of the test tubes immediately after adding ethanoic acid in each one of them, in which of the test tube or test tubes the flame will be extinguished?

(A) X and Y

(B) Y and Z

(C) X and Z

(D) only Z

In order to study saponification reaction, we first prepare 20% solution of sodium hydroxide. If we record the temperature of this solution just after adding sodium hydroxide flakes to water and also test its nature using litmus, it may be concluded that the process of making this solution is

(A) exothermic and the solution is alkaline

(B) endothermic and the solution is alkaline

(C) endothermic and the solution is acidic

(D) exothermic and the solution is acidic

While studying saponification reaction for the preparation of soap, a teacher suggested to a student to add a small quantity of common salt to the reaction mixture. The function of common salt in this reaction is to

(A) reduce the alkalinity of the soap

(B) reduce the acidity of the soap

(C) enhance the cleansing capacity of soap

(D) favour precipitation of soap

A student takes about 6 ml of distilled water in each of the four test tubes P, Q, R and S. He then dissolves an equal amount of four different salts namely, sodium chloride in 'P', potassium chloride in 'Q', calcium chloride in 'R' and magnesium chloride in 'S'. Next, he then adds 10 drops of soap solution to each test tube and shakes its contents. The test tubes in which scum (insoluble substance) is formed with soap are:

(A) P and Q

(B) Q and R

(C) R and S

(D) Q and S

You have four test tubes, A, B, C and D containing sodium carbonate, sodium chloride, lime water and blue litmus solutions respectively. Out of these the material of which test tube/ test tubes would be suitable for the correct test of acetic/ethanoic acid?

(a) only A
(b) A and B
(c) B and C
(d) A and D

A gas is liberated immediately with a brisk effervescence, when you add acetic acid to sodium hydrogen carbonate powder in a test tube. Name the gas and describe the test that confirms the identity of the gas. 

Complete the following chemical equations: C₂H₅OH+O₂→

Complete the following chemical equations : C₂H₅OH`("Conc."H_2SO_4)/(443K)`>

When you add a few drops of acetic acid to a test-tube containing sodium bicarbonate powder, which one of the following is your observation?

(A) No reaction takes place

(B) A colourless gas with pungent smell is released with brisk effervescence

(C) A brown coloured gas is released with brisk effervescence

(D) Formation of bubbles of a colourless and odourless gas

Draw the structure of butanoic acid.

A student takes 2 mL acetic acid in a dry test tube and adds a pinch of sodium hydrogen carbonate to it. He makes the following observations:

I. A colourless and odourless gas evolves with a brisk effervescence.

II. The gas turns lime water milky when passed through it.

III. The gas burns with an explosion when a burning splinter is brought near it.

IV. The gas extinguishes the burning splinter that is brought near it.

The correct observations are:

(A) I, II, and III

(B) II, III and IV

(C) III, IV and I

(D) IV, I and II

In an experiment to study the properties of acetic acid a student takes about 2 mL of acetic acid in a dry test tube. He adds about 2 mL of water to it and shakes the test tube well. He is likely to observe that:

(A) the acetic acid dissolves readily in water

(B) the solution becomes light orange

(C) water floats over the surface of acetic acid

(D) acetic acid floats over the surface of water

Study the different conclusions drawn by students of a class on the basis of observations of preserved/available specimens of plants and animals.

I. Potato and sweet potato are analogous organs in plants.

II. Wings of insects and wings of birds are homologous organs in animals.

III. Wings of insects and wings of bats are analogous organs in animals.

IV. Thorns of citrus and tendrils of cucurbita are analogous organs in plants.

The correct conclusions are:

(A) I, and II

(B) II and IV

(C) I and III

(D) III and IV

Answer the following question.
Write the chemical formula and name of the compound which is the active ingredient of all alcoholic drinks. List its two uses.

Write the chemical equation and name of the product formed when this compound reacts with -
(i) Sodium metal  
(ii) hot concentrated sulphuric acid