Atoms are defined as “the basic building blocks of matter”.
It is the smallest constituent unit of matter that possess the properties of the chemical element. Atoms don’t exist independently. Instead, they form ions and molecules which further combine in large numbers to form matter that we see, feel and touch.
A molecule is defined as the smallest unit of a compound that contains the chemical properties of the compound. Molecules are made up of groups of atoms.
Download PDF of Class 9 Chemistry Worksheet Chapter 3 Atoms and Molecules – Set 2
CBSE Class 9 Chemistry Worksheet Chapter 3 Atoms and Molecules – Set 2
Q1. A negatively charged ion is known as:
a.) cation
b.) anion
c.) polyatomic ion
d.) None of the above
Q2. An atom is similar to its ion in:
a.) nuclear charge
b.) mass number
c.) number of electrons
d.) number of neutrons
Q3. The chemical formula of water is:
a.) HO
b.) H2O
c.) O2H
d.) H3O
Q4. Who proposed the statement that the atom is indivisible?
a.) Rutherford
b.) Dalton
c.) Bohr
d.) Lavoisier
Q5. The smallest unit of a chemical compound is:
a.) Atom
b.) Ion
c.) Electron
d.) Molecule
Q6. Name the law of chemical combination which was given by:
a.) Lavoisier
b.) Proust
Q7. An element X has a valency of 1 and the other element Y has a valency of 2. What will the formula of its compound be?
Q8. How does an atom exist?
Q9. What is meant by the symbol of an element? Explain with examples.
Q10. What do you mean by the Law of constant proportions?
Q11. Hydrogen and oxygen combine in the ratio of 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3g of hydrogen gas?
Q12. Define polyatomic ions.
Q13. What is the chemical formula? Explain by giving examples.
Q14. Define 1 mole. Illustrate its relationship with the Avogadro constant.
Q15. Fill in the blanks.
a.) Mole is the link between the ___ atoms and the ___ atoms.
b.) A compound made up of only two elements is called a ____.
c.) Ionic compounds are formed by the combination between ____ and ____.
d.) If an atom has less electrons than normal, then it gets ____ charge.
e.) ____ represents the name of the substance.
Q16. Differentiate between:
a.) Atoms and molecules
b.) Cations and anions
c.) Molecular mass and molar mass
Q17. a.) In which one of the following cases is the number of hydrogen atoms is more?
Two moles of HCl or one mole of NH3.
b.) Calculate the mass of 1 mole of CaCO3.
c.) Give two examples of triatomic molecules.
Q18. a.) When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen? Which law of chemical combination will govern your answer?
b.) If one mole of carbon atoms weighs 12 grams, what is the mass (in grams) of 1 atom of carbon?
Q19. a.) Calculate the mole ratio of 240 g of calcium and 240 g of magnesium.
b.) If sulphur exists as S8 molecules, calculate the number of moles in 100 g of sulphur.
Q20. The mass of a single atom of an element X is 2.65 × 10–23 g. What is its atomic mass? What could this element be?
Download PDF to access answers of Chemistry Worksheet for Class 9 Chemistry Chapter 3 Atoms and Molecules Set – 2.
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Read Also:
- Difference Between An Atom And A Molecule
- Atoms and Molecules Questions
- Class 9 Chemistry Chapter 3 Atoms and Molecules MCQs
- Important Questions for Class 9 Science Chapter 3 – Atoms and Molecules
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