Chapter 1 some basic concepts of
chemistry
1 Mark Questions
Define chemistry.
Differentiate solids, liquids, and gases in terms of shape and volume.
Why are atomic masses of most elements fractional?
What is the SI unit of mole?
Round off to three significant figures: i) 35.296 ii) 12.2104
2 Mark Questions
Calculate the mass percent of elements in HNO₃.
Which law is obeyed when 4 L of N₂ reacts with 22.7 L of O₂ to form 45.4 L of N₂O? State the
law.
Which is preferred for expressing concentration: molality or molarity? Why?
Chlorine is prepared by treating MnO₂ with HCl. How many grams of HCl react with 5 g of
MnO₂? (Mn = 55, Cl = 35.5, O = 16).
Naphthalene contains 93.71% C and 6.29% H. If molar mass = 128 g/mol, calculate its
molecular formula.
3 Mark Questions
A 3 molal NaOH solution has density 1.110 g/mL. Calculate its molarity.
A nitric acid sample has density 1.41 g/mL and contains 69% HNO₃. Calculate molarity.
50 kg N₂ and 8 kg H₂ are mixed to form NH₃. Calculate NH₃ formed and identify the limiting
reagent.
Calculate the number of atoms in: i) 39 moles of He ii) 39 u of He iii) 39 g of He
4–5 Mark Questions (Conceptual + Numerical)
Calculate the mass percent of Ca, P, and O in Ca₃(PO₄)₂.
Derive the relationship between molarity and molality.
Explain the difference between empirical formula and molecular formula with examples.
A compound contains 4.07% H, 24.27% C, and 71.65% O. Its molar mass is 118 g/mol.
Determine empirical and molecular formula.
chemistry
1 Mark Questions
Define chemistry.
Differentiate solids, liquids, and gases in terms of shape and volume.
Why are atomic masses of most elements fractional?
What is the SI unit of mole?
Round off to three significant figures: i) 35.296 ii) 12.2104
2 Mark Questions
Calculate the mass percent of elements in HNO₃.
Which law is obeyed when 4 L of N₂ reacts with 22.7 L of O₂ to form 45.4 L of N₂O? State the
law.
Which is preferred for expressing concentration: molality or molarity? Why?
Chlorine is prepared by treating MnO₂ with HCl. How many grams of HCl react with 5 g of
MnO₂? (Mn = 55, Cl = 35.5, O = 16).
Naphthalene contains 93.71% C and 6.29% H. If molar mass = 128 g/mol, calculate its
molecular formula.
3 Mark Questions
A 3 molal NaOH solution has density 1.110 g/mL. Calculate its molarity.
A nitric acid sample has density 1.41 g/mL and contains 69% HNO₃. Calculate molarity.
50 kg N₂ and 8 kg H₂ are mixed to form NH₃. Calculate NH₃ formed and identify the limiting
reagent.
Calculate the number of atoms in: i) 39 moles of He ii) 39 u of He iii) 39 g of He
4–5 Mark Questions (Conceptual + Numerical)
Calculate the mass percent of Ca, P, and O in Ca₃(PO₄)₂.
Derive the relationship between molarity and molality.
Explain the difference between empirical formula and molecular formula with examples.
A compound contains 4.07% H, 24.27% C, and 71.65% O. Its molar mass is 118 g/mol.
Determine empirical and molecular formula.
