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Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Class 9 MCQ


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15 Questions MCQ Test Science Class 9 - Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules

Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules for Class 9 2024 is part of Science Class 9 preparation. The Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules questions and answers have been prepared according to the Class 9 exam syllabus.The Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules MCQs are made for Class 9 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules below.
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Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 1

Which of the following correctly represents 360g of water?
(i) 2 moles of water
(ii) 20 moles of water
(iii) 6.022 × 1023 molecules of water
(iv) 1.2044 × 1025 molecules of water

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 1

The molar mass of water (H2O) is approximately 18 g/mol.
For 360 g of water, the number of moles = 360 g / 18 g/mol = 20 moles.
Number of molecules = 20 moles × 6.022 × 1023 molecules/mole ≈ 1.2044 × 1025 molecules.

Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 2

1 u or 1 amu means

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 2

1 u (atomic mass unit) or 1 amu is defined as 1/12th of the mass of a carbon-12 atom.

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Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 3

Which of the following statements is not true about an atom?

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 3
  • Atoms are not always neutral
  • they can have charges when they become ions.
  • Additionally, atoms can exist independently, especially noble gases
  • Therefore, option 'd' is correct
Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 4

A sample of NH3 molecule irrespective of source contains 82.35% Nitrogen and 17.65% of Hydrogen by mass. This data supports:

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 4

The Law of Definite Proportions states that a compound always contains the same elements in certain fixed proportions by mass, regardless of its source or how it was prepared.

Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 5

Which of the following contains the maximum number of molecules?

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 5

The number of molecules in a sample is determined by Avogadro's number, which is the same for all substances. Hence, for a given mass, the substance with the smallest molar mass will have the most molecules. Among the options, H2 has the smallest molar mass.

Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 6

The molecular formula of potassium nitrate is ________.

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 6

Potassium nitrate has the chemical formula KNO3.

Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 7

An element X is divalent and another element Y is tetravalent. The compound formed by these two elements will be:

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 7

For the compound to be electrically neutral, the charges of the elements must balance. Given X is divalent (charge 2+) and Y is tetravalent (charge 4+), the compound will have the formula X2Y to balance the charges.

Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 8

Molecular mass is defined as the:

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 8

Molecular mass is the sum of the atomic masses of all atoms in a molecule, compared to the mass of a carbon-12 atom.

Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 9

3.42 g of sucrose are dissolved in 18 g of water in a beaker. The number of oxygen atoms in the solution is:

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 9

Calculate the number of moles of oxygen atoms in sucrose and water, then multiply by Avogadro's number to find the total number of oxygen atoms.

Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 10

The atomic mass of sodium is 23. The number of moles in 46g of sodium is ________.

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 10

Number of moles = Mass (in grams) / Molar mass.

Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 11

A change in the physical state can be brought about

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 11

Changing the physical state of matter typically requires energy input or removal to overcome intermolecular forces.

Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 12

What is the formula mass unit of ZnO?

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 12

The molar mass of ZnO can be calculated by summing the atomic masses of zinc and oxygen atoms.

Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 13

Which of the following represents a correct chemical formula?

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 13

BiPO4 represents bismuth(III) phosphate.

Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 14

Which of the following represents the correct relation between Avogadro's number (N0), number of particles (N), and moles (n)?

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 14

Avogadro's number represents the number of particles (atoms, molecules, ions) in one mole of a substance. Therefore, the number of moles (n) is equal to the number of particles (N) divided by Avogadro's number (No).

Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 15

How many atoms of oxygen are present in 300 grams of CaCO3?

Detailed Solution for Lakhmir Singh & Manjit Kaur Test: Atoms and Molecules - Question 15

Calculate the number of moles of CaCO3, then use Avogadro's number to find the number of oxygen atoms.

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