Chemistry

Question 1

What is the smallest particle of an element?

Answer 1

Atom

Question 2

Which option supports Dalton’s atomic theory?
a) Atoms of an element have identical mass.
- b) Atoms can be created by chemical reactions.
- c) Atoms of different elements have similar chemical properties.
- d) Atoms of an element change their properties in chemical reactions.

Answer 2

Atoms of an element have identical mass.

Question 3

The diagram below shows the molecule of urea. Which of the following statements is false?

Answer 3

c) Urea is a mixture

Question 4

Two elements A and B combine to form the compound AB2. Which of the following statements is true?
a) It is homogeneous.
- b) The properties of AB2 are different from A and B.
- c) It is a pure substance.
- d) All of these.

Answer 4

All of these

Question 5

Fullerene was discovered in 1985. It has a soccer ball-like structure with the chemical formula C60. From this information, which of the following is a correct statement about fullerene?

Answer 5

It consists of atoms of carbon only.

Question 6

Which of the following is the correct symbol of argon?

Answer 6

Ar

Question 7

Brass contains Cu and Zn. Which of the following is correct about brass?
a) Brass is an alloy, a homogeneous mixture of Cu and Zn.
- b) Brass is a compound of Cu and Zn.
- c) Brass contains Cu and Zn in a fixed ratio.
- d) All of these.

Answer 7

Brass is an alloy, a homogeneous mixture of Cu and Zn.

Question 8

The table shows the atomicity of different elements. Helium is monatomic. Oxygen is diatomic. Ozone is triatomic. Phosphorus is tetratomic. Why is ozone labeled as triatomic?
Because ozone can exist freely in nature.
- b) Because ozone is a gas and gases are triatomic.
- c) Because three atoms of oxygen combine to form ozone.
- d) Because three molecules of oxygen combine to form ozone.

Answer 8

Because three atoms of oxygen combine to form ozone.

Question 9

The symbol of tungsten is

Answer 9

W

Question 10

Which of the following is the correct molecule of phosphorus

Answer 10

P4

Question 11

All noble gases are:

Answer 11

Monatomic

Question 12

The maximum amount of element present in the human body is:

Answer 12

Oxygen

Question 13

Elements are made up of:

Answer 13

Atoms

Question 14

Which of the following proves the law of conservation of mass experimentally?**
- a) 12 g of CO reacts with 32 g of O2 to form 44 g of CO2.
- b) 1.70 g of AgNO3 reacts with 0.365 g of HCl to form 1.435 g of AgCl.
- c) 0.63 g of HNO3.
- d) 12 g of C is heated in a vacuum and on cooling there is no change in mass.
- e) 100 g of ice forms 100 g of water liquid on melting.

Answer 14

1.70 g of AgNO3 reacts with 0.365 g of HCl to form 1.435 g of AgCl.

Question 15

Identify the correct symbol of gold:

Answer 15

Au

Question 16

Identify the correct one from the following statements:**
- a) Elements can be changed into simpler substances.
- b) Compounds have variable composition.
- c) The mixture has properties similar to its components.
- d) Brass is a compound of copper and zinc.

Answer 16

The mixture has properties similar to its components

Question 17

The combining capacity of an element is called:

Answer 17

Valency

Question 18

18 g of water is electrolyzed. The weight of oxygen formed will be:

Answer 18

16g

Question 19

18 g of water is electrolyzed. The weight of oxygen formed will be:

Answer 19

16g

Question 20

The balancing of chemical equation is based on

Answer 20

Law of conservation of mass

Question 21

NaOH (aqueous) + HNO3 (aqueous) → NaNO3 (aqueous) + H2O (liquid). In this reaction, nitric acid acts as:

Answer 21

Acid

Question 22

Activity: Prepare a solution of barium chloride in water and take it in an ignition tube. Prepare a solution of sodium sulfate in water and take it in a conical glass flask. Hang the ignition tube in the flask carefully so that the solutions do not get mixed. Put the cork on the conical flask as shown in the figure. Weigh the flask with the contents carefully. Now tilt and shake the flask so that both solutions get mixed. Weigh again. Which law is verified by this activity?

Answer 22

Law of conservation of mass

Question 23

Which of the following is not a postulate of Dalton’s atomic theory?
All matter is made up of atoms.
- b) Atoms are tiny, indivisible, and indestructible ultimate particles.
- c) Atoms combine in the ratio of small whole numbers to form compounds.
- d) Atoms of different elements can have the same atomic mass.

Answer 23

Atoms of different elements can have the same atomic mass.

Question 24

X and Y are two elements which form X2Y3 and X3Y4. If 0.2 mol of X2Y3 weighs 32 grams and 0.4 mol of X3Y4 weighs 92.8 grams, the atomic weights of X and Y respectively are:

Answer 24

56, 16

Question 25

Which of the following is or are diatomic?

Answer 25

All of these