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Olympiad Test: Atoms and Molecules- 3 - Class 9 MCQ


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10 Questions MCQ Test Science Olympiad Class 9 - Olympiad Test: Atoms and Molecules- 3

Olympiad Test: Atoms and Molecules- 3 for Class 9 2024 is part of Science Olympiad Class 9 preparation. The Olympiad Test: Atoms and Molecules- 3 questions and answers have been prepared according to the Class 9 exam syllabus.The Olympiad Test: Atoms and Molecules- 3 MCQs are made for Class 9 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Olympiad Test: Atoms and Molecules- 3 below.
Solutions of Olympiad Test: Atoms and Molecules- 3 questions in English are available as part of our Science Olympiad Class 9 for Class 9 & Olympiad Test: Atoms and Molecules- 3 solutions in Hindi for Science Olympiad Class 9 course. Download more important topics, notes, lectures and mock test series for Class 9 Exam by signing up for free. Attempt Olympiad Test: Atoms and Molecules- 3 | 10 questions in 20 minutes | Mock test for Class 9 preparation | Free important questions MCQ to study Science Olympiad Class 9 for Class 9 Exam | Download free PDF with solutions
Olympiad Test: Atoms and Molecules- 3 - Question 1
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The mass of a single atom of an element Z is 2.65 × 10–23g. What is its gram atomic mass?

Detailed Solution for Olympiad Test: Atoms and Molecules- 3 - Question 1
The mass of one atom of an element Z = 2.65×10–23 g

We know that 1 mole of an atom = 6.023×1023 atoms

1 mole of an atom = its atomic weight

Mass of one atom of an element = 2.65×10–23 g

Mass of 6.023×1023 atoms of an element Z = 2.65×10–23 ×6.023×1023 g =15.69 g

Olympiad Test: Atoms and Molecules- 3 - Question 2
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In 8O16, the number 16 stands for

Detailed Solution for Olympiad Test: Atoms and Molecules- 3 - Question 2
16 stands for Atomic mass of Oxygen.
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Olympiad Test: Atoms and Molecules- 3 - Question 3
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The best standard for atomic mass is

Detailed Solution for Olympiad Test: Atoms and Molecules- 3 - Question 3
An atomic mass unit (symbolized amu) is defined as precisely 1/12 the mass of an atom of carbon-12. The carbon-12 (C-12) atom has six protons and six neutrons in its nucleus.
Olympiad Test: Atoms and Molecules- 3 - Question 4
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All samples of carbon dioxide contain carbon and oxygen in the mass ratio of 3 : 8. This is in agreement with the law of
Detailed Solution for Olympiad Test: Atoms and Molecules- 3 - Question 4

In CO2, 12 g of carbon combines with 32 of oxygen.

12/32 = 3/8 = 3.8

Therefore, weight ratio of carbon to oxygen is 3:8. This is in agreement with the law of definite proportion.

Olympiad Test: Atoms and Molecules- 3 - Question 5
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A compound has the following percentage composition (H = 2.04%, S = 32.65%, O = 65.31%.

Relative molecular mass of compound = 98. What will be its molecular formula (H = 1, S = 32, O = 16)
Detailed Solution for Olympiad Test: Atoms and Molecules- 3 - Question 5

  • The first step in this problem is to change the % to grams.

    32.65%→32.65g of S

    65.3%→65.3g of O

    2.04%→2.04g of H

  • Next divide all the given masses by their molar mass.

    32.65g of S/ 32gm-1 = 1.0203 moles of S

    65.3g of O/ 16gm-1 = 4.08 moles of O

    2.04g of H/ 1.008gm-1 = 2.024 moles of H

  • Then, pick the smallest answer in moles from the previous step and divide all the answers by that. Remember that if you calculate a number that is x0.9 round to the nearest whole number

    1.0203 moles of S/ 1.0203 = 1

    4.08 moles of O/1.0203 = 3.998 ≈ 4

    2.024 moles of H/1.0203 = 1.984 ≈ 2

  • Lastly, the coefficients calculated in the previous step will become the subscripts in the chemical formula.

    S = 1

    O = 4

    H = 2

    H2SO4

Olympiad Test: Atoms and Molecules- 3 - Question 6
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Modern atomic symbol was proposed by
Detailed Solution for Olympiad Test: Atoms and Molecules- 3 - Question 6
Modern atomic symbol was proposed by Berzelius.
Olympiad Test: Atoms and Molecules- 3 - Question 7
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How many moles are present in 12.044 × 1022 molecules of sulphur dioxide?
Detailed Solution for Olympiad Test: Atoms and Molecules- 3 - Question 7

We know that :

6.022×1023 molecules of Sulphur Dioxide = 1 mole

So, 12.044×1022 molecules of Sulphur Dioxide

= 1/6.022×1023 × 12.044×1022

= 2/10

= 0.2 mole

Thus, 12.044×1023 molecules of Sulphur Dioxide are 0.2 mole.

Olympiad Test: Atoms and Molecules- 3 - Question 8
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What will be the atoms in 0.2 mole of sodium (Na)
Detailed Solution for Olympiad Test: Atoms and Molecules- 3 - Question 8

Given: 0.2moles of sodium.

To find: We have to find the number of atoms.

Solution:

To determine the number of atoms we have to follow the below steps-

Sodium is an alkali metal. It has the symbol Na.

It has the atomic number 11.

It has a mass of 23.

1 mole of sodium contains 6.023×1023 number of atoms.

Thus 0.2 moles of sodium will contain

6.023×1023 × 0.2 = 1.20×1023 number of atoms.

Thus 0.2 moles of sodium contains 1.2×1023 i.e., 13.054 × 1022 number of atoms.

Olympiad Test: Atoms and Molecules- 3 - Question 9
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The symbol of a metal element which is used in making thermometers is:
Detailed Solution for Olympiad Test: Atoms and Molecules- 3 - Question 9
Metal element which is used in making thermometers is Mercury. Its symbol is Hg.
Olympiad Test: Atoms and Molecules- 3 - Question 10
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The mass of a single atom of an element X is 2.65 × 10–23 g. what is its atomic mass?
Detailed Solution for Olympiad Test: Atoms and Molecules- 3 - Question 10
The mass of one atom of an element X = 2.65×10–23 g

We know that 1 mole of an atom = 6.023×1023 atoms

1 mole of an atom = its atomic weight

Mass of one atom of an element = 2.65×10–23 g

Mass of 6.023×1023 atoms of an element Z = 2.65×10–23 ×6.023×1023 g =15.69 g

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