Every Book Back multiple-choice question from Atoms and Molecules (10th Standard Science, Samacheer Kalvi) — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
Which of the following has the smallest mass?
- A. \(6.023 \\times 10^{23}\) atoms of He
- B. 1 atom of HeCorrect
- C. 2 g of He
- D. 1 mole atoms of He
Explanation. One helium atom has a mass of only 4 amu, which is extremely small (about \(6.64 \\times 10^{-24}\) g) compared to one mole of helium atoms or two grams of helium, which are macroscopic quantities.
Q2
Which of the following is a triatomic molecule?
- A. Glucose
- B. Helium
- C. Carbon dioxideCorrect
- D. Hydrogen
Explanation. Carbon dioxide (\(CO_2\)) is a triatomic molecule because it consists of three atoms in total: one carbon atom and two oxygen atoms chemically bonded together.
Q3
The volume occupied by 4.4 g of \(CO_2\) at S.T.P is
- A. 22.4 litre
- B. 2.24 litreCorrect
- C. 0.24 litre
- D. 0.1 litre
Explanation. The molecular mass of carbon dioxide is 44 g/mol. Therefore, 4.4 g represents 0.1 mol. Since one mole of gas occupies 22.4 L at STP, 0.1 mol occupies 2.24 L.
Q4
Mass of 1 mole of Nitrogen atom is
- A. 28 amu
- B. 14 amu
- C. 28 g
- D. 14 gCorrect
Explanation. The mass of one mole of nitrogen atoms is equal to its gram atomic mass. Since the atomic mass of nitrogen is 14, one mole of nitrogen atoms weighs 14 g.
Q5
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 atomCorrect
- D. Mass of O - 16 atom
Explanation. An atomic mass unit (amu) is defined as exactly one-twelfth of the mass of a carbon-12 atom, which is used as the standard reference scale in chemistry.
Q6
Which of the following statements is incorrect?
- A. 12 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.Correct
- D. One mole of electrons stands for \(6.023 \\times 10^{23}\) electrons.
Explanation. Hydrogen gas (\(H_2\)) is diatomic. Therefore, one mole of hydrogen gas contains Avogadro's number of molecules, which corresponds to two moles (\(2 \\times 6.023 \\times 10^{23}\)) of individual hydrogen atoms.
Q7
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 litreCorrect
- D. 44.8 litre
Explanation. According to Avogadro's hypothesis, one mole of any gas, whether monoatomic, diatomic, or polyatomic, occupies a standard molar volume of 22.4 litres at standard temperature and pressure.
Q8
In the nucleus of \(_{20}Ca^{40}\), there are
- A. 20 protons and 40 neutrons
- B. 20 protons and 20 neutronsCorrect
- C. 20 protons and 40 electrons
- D. 40 protons and 20 electrons
Explanation. For calcium with atomic number 20 and mass number 40, the number of protons is 20, and the number of neutrons is the mass number minus the atomic number, which is 20.
Q9
The gram molecular mass of oxygen molecule is
- A. 16 g
- B. 18 g
- C. 32 gCorrect
- D. 17 g
Explanation. An oxygen molecule is diatomic (\(O_2\)). Since the atomic mass of oxygen is 16, its gram molecular mass is calculated as \(2 \\times 16\) g, which equals 32 g.
Q10
1 mole of any substance contains ______________ molecules.
- A. \(6.023 \\times 10^{23}\)Correct
- B. \(6.023 \\times 10^{-23}\)
- C. \(3.0115 \\times 10^{23}\)
- D. \(12.046 \\times 10^{23}\)
Explanation. By definition, one mole of any substance contains Avogadro's number of elementary entities, which is equal to \(6.023 \\times 10^{23}\) molecules.
About these Atoms and Molecules questions
These are the Book Back multiple-choice questions for Atoms and Molecules from the Tamil Nadu State Board (Samacheer Kalvi) 10th Standard Science syllabus. Each question shows the correct option and an original, step-by-step explanation so you understand the method, not just the answer. Use the answer key above to jump to any question, then take the practice test to check yourself under exam-like conditions.
Frequently asked questions
How many MCQs are there in Atoms and Molecules?
This chapter has 10 book-back multiple-choice questions, each with the correct answer and a step-by-step explanation.
Are these 10th Standard Science MCQs free to practise online?
Yes. Every question, answer and explanation here is free, and you can also take them as a timed practice test.
Where can I find the Atoms and Molecules book-back answers?
The correct option for each question is highlighted on this page with a worked explanation, plus a quick answer-key summary at the top.
