1.21. The following data were obtained when dinitrogen and dioxygen react together to form compounds: (Beginner)

Mass of dinitrogen             Mass of dioxygen

(i) 14 g                               16 g

(ii) 14 g                              32 g

(iii) 28 g                             32 g

(iv) 28 g                             80 g

(a) Which law of chemical combination is obeyed by the above experimental data? Give its statement.

(b) Fill in the blanks in the following conversions:

(i) 1 km = ...................... mm = ...................... pm

(ii) 1 mg = ...................... kg = ...................... ng

(iii)1 mL = ...................... L = ...................... dm3

In the medical entrance test NEET, there can be 1 to 3 questions from this chapter. Some year, the Chemistry section of NEET has only one question from this chapter and in some other years, there can be 3 questions.

The following are the key concepts of this chapter: Compound, Elements, Rules, Law of conservation of mass, Addition and Subtraction, Atomic Mass, Law of multiple proportions, and Molecular Mass.

As the name suggests, the first chapter of the NCERT Class 11 Chemistry introduces various basic concepts of chemistry, such as the definition and importance of chemistry, atomic matter and molecular masses, the mole concept, laws of chemical combination, empirical, stoichiometry, and molecular form