Atoms and Molecules
The molar mass of a substance is the mass of 1 mole of that substance.
It is equal to the 6.022 × 1023 atoms of that element/substance.
A group of 6.022 × 1023 particles (atoms, molecules or ions) of a substance
is called a mole of that substance.
VERY SHORT ANSWER TYPE QUESTIONS
1. Write full form of IUPAC.
2. Name the scientist who gave atomic theory of matter.
3. What are building blocks of matter ?
4. Name two laws of chemical combination.
5. Name the unit in which atomic radius is usually expressed.
6. Define molecular mass.
7. What is formula unit mass ?
8. Name the element used as standard for atomic mass scale.
SHORT ANSWER TYPE QUESTIONS
1. What is atomicity ? Explain with two examples.
2. State law of conservation of mass.
3. State law of constant proportion.
4. Calculate molecular mass of H2 and NH3. (At. mass of H = 1 u, N = 14 u)
LONG ANSWER TYPE QUESTIONS
1. Write postulates of Dalton’s atomic theory.
2. What is the difference between molecule of an element and the molecule of
a compound ? Give one example of each.
1. In what form does oxygen gas occur in nature ?
2. In what form do noble gases occur in nature ?
3. What is the difference between 2H and H2 ?