class9 Atoms and Molecules multiple choice questions (25 MCQ's)

Clasa 9 Science ! 

Here's a multiple-choice quiz based on chapter Atoms and Molecules chemistry class 9

🎈Topic 

🎈Dalton's Atomic Theory:

1. Who is credited with the development of Dalton's Atomic Theory?

   a) John Dalton

   b) Albert Einstein

   c) Isaac Newton

   d) Marie Curie

2. According to Dalton's Atomic Theory, atoms are:

   a) Indivisible

   b) Composed of protons, neutrons, and electrons

   c) Made up of smaller particles called quarks

   d) Always in a state of motion

3. Dalton's Atomic Theory states that all atoms of a given element are:

   a) Identical

   b) Different in size and mass

   c) Different in chemical properties

   d) Composed of protons and electrons

4. In Dalton's Atomic Theory, compounds are formed by:

   a) Mixing atoms of different elements together

   b) Breaking atoms into smaller particles

   c) Combining atoms in simple, whole-number ratios

   d) Randomly arranging atoms

5. Which part of Dalton's Atomic Theory was later modified due to the discovery of isotopes?

   a) Atoms are indivisible.

   b) Atoms of different elements have different properties.

   c) Atoms combine in simple, whole-number ratios.

   d) Atoms of the same element are identical.

Answers:

1. a) John Dalton

2. a) Indivisible

3. a) Identical

4. c) Combining atoms in simple, whole-number ratios

5. d) Atoms of the same element are identical.

🎈Topic : Chemical Laws of Combination:

1. Which scientist is credited with the discovery of the Law of Definite Proportions?

   a) John Dalton

   b) Antoine Lavoisier

   c) Dmitri Mendeleev

   d) Robert Boyle

2. The Law of Definite Proportions states that:

   a) Elements can combine in any ratio to form compounds.

   b) The mass of one element in a compound is always a whole number ratio to the mass of another element in the same compound.

   c) Elements can combine in any proportion, and the resulting compound will have varying properties.

   d) The mass of an element in a compound is always the same, regardless of the elements involved.

3. Which law of chemical combination is also known as the Law of Multiple Proportions?

   a) Law of Conservation of Mass

   b) Law of Definite Proportions

   c) Law of Combining Volumes

   d) Avogadro's Law

4. The Law of Combining Volumes, formulated by Gay-Lussac, states that when gases react, they do so in volumes that are in simple whole number ratios. What is an example of this law in action?

   a) The combination of hydrogen and oxygen to form water

   b) The formation of carbon dioxide from carbon and oxygen

   c) The decomposition of ammonia into nitrogen and hydrogen

   d) The reaction of sulfur with oxygen to produce sulfur dioxide

5. According to the Law of Conservation of Mass, in a chemical reaction:

   a) Mass can be created or destroyed.

   b) The total mass of the reactants is equal to the total mass of the products.

   c) The total mass of the reactants is always greater than the total mass of the products.

   d) The total mass of the products is always greater than the total mass of the reactants.

Answers:

1. a) John Dalton

2. b) The mass of one element in a compound is always a whole number ratio to the mass of another element in the same compound.

3. c) Law of Combining Volumes

4. a) The combination of hydrogen and oxygen to form water

5. b) The total mass of the reactants is equal to the total mass of the products.

🎈 Topics of the Law of Conservation of Mass and the Law of Constant Proportions:

1. The Law of Conservation of Mass states that:

   a) Mass is always created in a chemical reaction.

   b) Mass can be destroyed in a chemical reaction.

   c) Mass is neither created nor destroyed in a chemical reaction.

   d) Mass changes depending on the elements involved.

2. Who is credited with the formulation of the Law of Conservation of Mass?

   a) Antoine Lavoisier

   b) John Dalton

   c) Dmitri Mendeleev

   d) Albert Einstein

3. According to the Law of Constant Proportions:

   a) Elements can combine in various proportions to form compounds.

   b) The mass of one element in a compound is always a whole number ratio to the mass of another element in the same compound.

   c) The mass of elements in a compound can vary over time.

   d) Compounds are always composed of the same elements in the same proportions by mass.

4. Which law is also known as the Law of Definite Proportions?

   a) Law of Conservation of Mass

   b) Law of Constant Proportions

   c) Law of Combining Volumes

   d) Avogadro's Law

5. If you have a sample of water (H2O), which law would best describe the composition of this compound?

   a) Law of Conservation of Mass

   b) Law of Multiple Proportions

   c) Law of Constant Proportions

   d) Gay-Lussac's Law

Answers:

1. c) Mass is neither created nor destroyed in a chemical reaction.

2. a) Antoine Lavoisier

3. d) Compounds are always composed of the same elements in the same proportions by mass.

4. b) Law of Constant Proportions

5. c) Law of Constant Proportions

🎈Topics Atomic number, atomic mass, isobars, and isotopes:

1. The atomic number of an element is defined as:

   a) The number of neutrons in the nucleus.

   b) The total number of protons and neutrons in the nucleus.

   c) The number of protons in the nucleus.

   d) The number of electrons in the electron cloud.

2. What does the atomic mass of an element represent?

   a) The number of electrons in the element.

   b) The combined mass of protons and electrons.

   c) The average mass of all naturally occurring isotopes of the element.

   d) The total number of particles in the nucleus.

3. Isotopes of an element have the same number of:

   a) Protons and electrons.

   b) Electrons but different numbers of protons.

   c) Protons but different numbers of neutrons.

   d) Neutrons but different numbers of protons.

4. Isotopes of an element differ in:

   a) Atomic number.

   b) Atomic mass.

   c) Both atomic number and atomic mass.

   d) Chemical properties.

5. Isobars are atoms or ions that have:

   a) The same number of protons but different numbers of electrons.

   b) The same atomic number but different atomic masses.

   c) The same number of neutrons but different atomic masses.

   d) The same number of protons and neutrons.

Answers:

1. c) The number of protons in the nucleus.

2. c) The average mass of all naturally occurring isotopes of the element.

3. c) Protons but different numbers of neutrons.

4. b) Atomic mass.

5. b) The same atomic number but different atomic masses.

Certainly! Here are some additional multiple-choice questions on the topics of atomic number, atomic mass, isobars, and isotopes:

6. The atomic number of an element determines:

   a) The chemical properties of the element.

   b) The mass of the element.

   c) The number of neutrons in the nucleus.

   d) The number of electrons in the electron cloud.

7. Which subatomic particle is responsible for the identity of an element?

   a) Protons

   b) Neutrons

   c) Electrons

   d) Positrons

8. If an element has an atomic number of 8, how many electrons does it have in its electron cloud?

   a) 8

   b) 16

   c) 0

   d) It varies depending on the isotope.

9. Which term describes atoms or ions with the same atomic mass but different atomic numbers?

   a) Isomers

   b) Isotopes

   c) Isobars

   d) Isotones

10. The atomic mass unit (amu) is defined as:

    a) The mass of one proton.

    b) The mass of one neutron.

    c) 1/12th the mass of a carbon-12 atom.

    d) The mass of one electron.

Answers:

6. a) The chemical properties of the element.

7. a) Protons

8. a) 8

9. c) Isobars

10. c) 1/12th the mass of a carbon-12 atom.

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