Atoms and Molecules

Topics in this chapter

• Atomic Theory and History
• Laws of Chemical Combination
• Atoms, Molecules, and Atomicity
• Mole Concept and Masses
• Valency and Chemical Formulae
• Chemical Equations and Balancing

Cheat sheet

Practice questions

1. Question 1Q-0BE758

   Which of the following represents the correct chemical formula of aluminium sulphate?

   1. A.AlSO4
   2. B.Al2(SO4)3
   3. C.Al3(SO4)2
   4. D.Al2SO4
   See the answer and solution
2. Question 2Q-2D7E10

   What is the mass of 0.5 mole of nitrogen gas ($N_2$)?

   1. A.7 g
   2. B.14 g
   3. C.28 g
   4. D.56 g
   See the answer and solution
3. Question 3Q-07164A

   According to the Law of Conservation of Mass, what happens during a chemical reaction?

   1. A.Total mass increases
   2. B.Total mass decreases
   3. C.Total mass remains unchanged
   4. D.Mass gets converted into energy completely
   See the answer and solution
4. Question 4Q-068C0B

   Which of the following elements is diatomic?

   1. A.Argon
   2. B.Sodium
   3. C.Oxygen
   4. D.Phosphorus
   See the answer and solution
5. Question 5Q-47FAD1

   What is the molecular mass of water ($H_2O$)? (Given atomic masses: $H = 1\text{ u}$, $O = 16\text{ u}$)

   1. A.17 u
   2. B.18 u
   3. C.16 u
   4. D.34 u
   See the answer and solution