Class 11 Chemistry Chapter 1 - Some Basic Concepts of Chemistry MCQs
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Answer: (a) Mole
The mole is the SI unit for amount of substance, representing 6.022 × 10²³ entities.
Answer: (c) CH₂O
The empirical formula shows the simplest whole-number ratio of elements: CH₂O.
Answer: (b) 18 g/mol
Molar mass = (2 × 1) + 16 = 18 g/mol.
Answer: (b) 6.022 × 10²³
Avogadro's number equals the number of particles in one mole.
Answer: (c) Mass can neither be created nor destroyed
In a chemical reaction total mass remains constant.
Answer: (d) All of the above
One mole contains 6.022 × 10²³ entities — atoms, molecules, or ions.
Answer: (c) C₆H₁₂O₆
Glucose has molecular formula C₆H₁₂O₆.
Answer: (c) Atomic mass is the same as atomic number
Atomic mass differs from atomic number (which equals proton count).
Answer: (c) Law of constant composition
A compound always contains the same proportion of elements by mass.
Answer: (b)
Mass percent = (number of atoms × atomic mass / molar mass of compound) × 100.
Answer: (a) 22.4 L
At STP one mole of an ideal gas occupies 22.4 liters.
Answer: (d) C₄H₁₀
As carbon content increases with carbon chain length among these, C₄H₁₀ has the highest %C here.
Answer: (a) An element
An element consists of only one type of atom.
Answer: (d) Both (a) and (c)
Molecular weight equals the sum of atomic weights and also the mass of one mole of molecules.
Answer: (a) Mass per unit volume
Density = mass / volume.
Answer: (b) The simplest whole-number ratio of atoms in the compound
Empirical formula gives the simplest ratio of elements.
Answer: (d) Light
Light is a form of energy, not a state of matter.
Answer: (c) Both (a) and (b)
Atoms or molecules can participate in chemical reactions depending on the process.
Answer: (b) Number of particles in a mole
Avogadro constant gives the number of atoms, ions or molecules in one mole.
Answer: (c) 2
Leading zeros are not significant; only '5' and '1' are significant here.