English Medium Class 10 - CBSE Important Questions for Science

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

List two differences between the properties exhibited by covalent compounds and ionic compounds.

Assertion (A): Melting point and boiling point of ethanol are lower than that of sodium chloride.

Reason (R): The forces of attraction between the molecules of ionic compounds are very strong.

Name the compound formed when ethanol is heated at 443 K in the presence of conc. \[\ce{H2SO4}\] and draw its electron dot structure.

State the role of conc. \[\ce{H2SO4}\] in the reaction.

The electron dot structure of chlorine molecule is:

Why is glacial acetic acid called so?

What happens when ethanol is heated at 443K in the presence of conc. H₂SO₄? Write the role of conc. H₂SO₄ in this case.

Write an equation showing saponification.

Write the chemical equation for the following:

Esterification Reaction