Atoms and Molecules

Samacheer Book Back Questions And Answers For Science Standard 10 “Atoms and Molecules“

I. Choose the best answer:
1. Which of the following has the smallest mass?
a. 6.023 × 10²³ atoms of He
b. 1 atom of He
c. 2 g of He
d. 1 mole atoms of He

2. Which of the following is a triatomic molecule?
a. Glucose
b. Helium
c. Carbon dioxide
d. Hydrogen

3. The volume occupied by 4.4 g of CO₂ at S.T.P
a. 22.4 litre
b. 2.24 litre
c. 0.24 litre
d. 0.1 litre

4. Mass of 1 mole of Nitrogen atom is
a. 28 amu
b. 14 amu
c. 28 g
d. 14 g

5. Which of the following represents 1 amu?
a. Mass of a C – 12 atom
b. Mass of a hydrogen atom
c. 1/12th of the mass of a C – 12 atom
d. Mass of O – 16 atom

6. Which of the following statement is incorrect?
a. One gram of C – 12 contains Avogadro’s number of atoms.
b. One mole of oxygen gas contains Avogadro’s number of molecules.
c. One mole of hydrogen gas contains Avogadro’s number of atoms.
d. One mole of electrons stands for 6.023 × 1023 electrons.

7. The volume occupied by 1 mole of a diatomic gas at S.T.P is
a. 11.2 litre
b. 5.6 litre
c. 22.4 litre
d. 44.8 litre

8. In the nucleus of ₂₀Ca⁴⁰, there are
a. 20 protons and 40 neutrons
b. 20 protons and 20 neutrons
c. 20 protons and 40 electrons
d. 40 protons and 20 electrons

9. The gram molecular mass of oxygen molecule is _____.
a. 16 g
b. 18 g
c. 32 g
d. 17 g

10. 1 mole of any substance contains ____ molecules.
a. 6.023 × 10²³
b. 6.023 × 10^-23
c. 3.0115 × 10²³
d. 12.046 × 10²³

II. Fill in the blanks:
1. Atoms of different elements having _____ mass number, but _____ atomic numbers are called isobars.
2. Atoms of different elements having same number of _____ are called isotones.
3. Atoms of one element can be transmuted into atoms of other element by _____.
4. The sum of the numbers of protons and neutrons of an atom is called its _____.
5. Relative atomic mass is otherwise known as _____.
6. The average atomic mass of hydrogen is _____ amu.
7. If a molecule is made of similar kind of atoms, then it is called _____ atomic molecule.
8. The number of atoms present in a molecule is called its _____.
9. One mole of any gas occupies _____ ml at S.T.P
10. Atomicity of phosphorous is _____.

Answers:
1. same, different
2. neutrons
3. artificial transmutation
4. mass number
5. standard atomic weight
6. 1.0079
7. Homo
8. atomicity
9. 22400
10. 4

III. Match the following:
1. 8 g of O2           A. 4 moles
2. 4 g of H2           B. 0.25 moles
3. 52 g of He         C. 2 moles
4. 112 g of N2       D. 0.5 moles
5. 35.5 g of Cl2      E. 13 moles

Answers:
1. B
2. C
3. E
4. A
5. D

IV. True or False: (If false give the correct statement)
1. Two elements sometimes can form more than one compound.
2. Noble gases are Diatomic.
3. The gram atomic mass of an element has no unit.
4. 1 mole of Gold and Silver contain same number of atoms –
5. Molar mass of CO₂ is 42g.

Answers:
1. True
2. False (Noble gases are monoatomic)
3. False (The gram atomic mass of an element is exposed in grams)
4. True
5. False (Molar mass of CO₂ is 44g)

V. Assertion and Reason:
1. Assertion: Atomic mass of aluminium is 27
Reason: An atom of aluminium is 27 times heavier than 1/12th of the mass of the C – 12 atom.
a) A and R are correct, R explains the A.
b) A is correct, R is wrong.
c) A is wrong, R is correct.
d) A and R are correct, R doesn’t explains A.

2. Assertion: The Relative Molecular Mass of Chlorine is 35.5 a.m.u.
Reason: The natural abundance of Chlorine isotopes are not equal.
a) A and R are correct, R explains the A.
b) A is correct, R is wrong.
c) A is wrong, R is correct.
d) A and R are correct, R doesn’t explains A.

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