Chemistry Questions on Mole Concepts for Class 9

By Jitender Singh on Feb 9, 2023

The mole, symbol mol, is the SI unit of amount of substance. One mole contains $N_A=6.022\times10^{23}$ elementary entities (atom, molecule, etc). This number is called the Avogadro number. Thus, one mole of H atoms is $6.022\times10^{23}$ atoms of hydrogen and one mole of H₂ molecules is $6.022\times10^{23}$ molecules of water.

1. In a reaction, 5.3 g of sodium carbonate reacted with 6 g of acetic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium acetate. Write the chemical equation for this reaction. Show that law of conservation of mass is true for this reaction.
2. Hydrogen and oxygen combine in the ratio of 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
3. Calculate the molecular mass of water H₂O, HNO₃, H₂, O₂, Cl₂, CO₂, CH₄, C₂H₆, C₂H₄, NH₃, CH₃OH, C₂H₂, S₈, P₄, HCl.
4. Calculate the formula unit mass of CaCl₂, ZnO, Na₂O, and K₂CO₃.
5. Calculate the number of moles for the (i) 52 g of He (ii) $12.044 \times 10^{23}$ number of He atoms.
6. Calculate the mass of the (i) 0.5 mole of N₂ gas (ii) 0.5 mole of N atoms (iii) $3.011\times 10^{23}$ number of N atoms (iv) $6.022\times10^{23}$ number of N₂ molecules.
7. Calculate the number of particles in (i) 46 g of Na atoms (ii) 8 g O₂ molecules (iii) 0.1 mole of carbon atoms
8. If one mole of carbon atoms weighs 12 grams, what is the mass (in grams) of 1 atom of carbon?
9. Which has more number of atoms, 100 grams of sodium or 100 grams of iron?
10. A 0.24 g sample of compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. Calculate the percentage composition of the compound by weight.
11. When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen?
12. What is the mass of (i) 1 mole of nitrogen atoms? (ii) 4 moles of aluminium atoms (iii) 10 moles of sodium sulphite (Na₂SO₃)?
13. Convert into mole (i) 12 g of oxygen gas (ii) 20 g of water (iii) 22 g of carbon dioxide
14. What is the mass of (i) 0.2 mole of oxygen atoms? (ii) 0.5 mole of water molecules?
15. Calculate the number of molecules of sulphur (S₈) present in 16 g of solid sulphur.
16. Calculate the number of aluminium ions present in 0.051 g of aluminium oxide.
17. How many grams of carbon is there in 1 mole of carbon dioxide?
18. Beryllium is a light metal used to fabricate transparent X-ray windows for medical imaging instruments. How many moles of Be are in a thin-foil window weighing 3.24 g?
19. What is the mass of 2.561 mol of gold?
20. How many moles of sucrose, C₁₂H₂₂O₁₁, are in a 25-g sample of sucrose?
21. Vitamin C is a covalent compound with the molecular formula C₆H₈O₆. The recommended daily dietary allowance of vitamin C for children aged 4–8 years is $1.42\times10^{-4}$ mol. What is the mass of this allowance in grams?
22. A packet of an artificial sweetener contains 40.0 mg of saccharin (C₇H₅NO₃S). Given that saccharin has a molar mass of 183.18 g/mol, how many saccharin molecules are in a 40.0 mg sample of saccharin? How many carbon atoms are in the same sample?