Atoms are described as “the fundamental building blocks of matter.”
It is the smallest constituent unit of matter that possesses chemical element properties. Atoms do not exist in isolation; instead, they combine to form ions and molecules, which then combine in large numbers to form the matter we see, feel, and touch.
A molecule is the smallest unit of a compound that contains the compound’s chemical properties. Molecules are made up of atom groups. One or more atoms make up a molecule. If they have more than one atom, they can be the same (for example, an oxygen molecule has two oxygen atoms) or different (a water molecule has two hydrogen atoms and one oxygen atom).
Download PDF of Class 9 Chemistry Worksheet on Chapter 3 Atoms and Molecules – Set 3
CBSE Class 9 Chemistry Worksheet Chapter 3 Atoms and Molecules – Set 3
Q1. One nm is equal to:
a.) 10–9 mm
b.) 10–7 cm
c.) 10–9 cm
d.) 10–6 m
Q2. In water, the proportion of oxygen and hydrogen by mass is:
a.) 1: 4
b.) 1: 8
c.) 4 : 1
d.) 8 : 1
Q3. Molecular compounds are usually formed by the combination between:
a.) a metal and a non-metal
b.) two different non-metals
c.) two different metals
d.) any two gaseous elements
Q4. Which of the following has the maximum number of atoms?
a.) 18 g of H2O
b.) 18 g of O2
c.) 18 g of CO2
d.) 18 g of CH4
Q5. The number of moles in 2 × 1024 atoms of iron are:
a.) 3.3
b.) 4.5
c.) 5.2
d.) 2.1
Q6. Define molecule.
Q7. State True or False.
a.) A sodium ion has a positive charge because it has more protons than a neutral atom.
b.) A chloride ion has a negative charge because it has more electrons than a neutral atom.
Q8. Give three significance of mole
Q9. Define valency.
Q10. What is Avogadro’s constant?
Q11. Define the term gram atom. How is it related to mole and Avogadro number?
Q12. State the postulates of Dalton’s atomic theory.
Q13. What is a mole? What is the unit of a mole? How many molecules are there in a certain mass of a substance?
Q14. Write the name of the following compounds. Also, show the ions present in them:
a.) Al2(SO4)3
b.) CaCl2
c.) K2SO4
d.) KNO3
e.) CaCO3
Q15. An element X forms an oxide XO3.
a.) What is the valency of element X?
b.) What will be the formula of chloride of X?
Q16. What are ionic and molecular compounds? Give examples.
Q17. a.) Define atomicity.
b.) Write the atomicity of the following:
i.) I2
ii.) H2S
iii.) HNO3
iv.) Na2SO4
V.) S8
Q18. a.) Why the definition of an atom given by Dalton is no longer valid?
b.) Why is necessary to use symbols for the elements?
c.) Name any two elements whose symbols do not start with the same letter as that of the name of the element.
Q19. a.) Differentiate between formula unit mass and molecular mass.
b.) Calculate the molar mass of the following compounds:
i.) MgO
ii.) Na2CO3
iii.) H3PO4
iv.) Ca(OH)2
Q20. Calculate the number of particles in each of the following:
a.) 46 g of Na atoms
b.) 8 g of O2 molecules
c.) 0.1 moles of carbon atoms
Download PDF to access answers of Chemistry Worksheet for Class 9 Chemistry Chapter 3 Atoms and Molecules Set – 3.
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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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