NCERT: Atoms and Molecules

Focusing on the "grammar" of chemistry, this set evaluates the rules for writing and naming chemical compounds. Based on the Chapter 9 Answer Key, the questions require students to identify cations (positive ions) and anions (negative ions) and use them to construct correct chemical formulae like $Al(NO_3)_3$ (Aluminum Nitrate) or $Fe_2O_3$ (Iron III Oxide). Students will perform calculations for formula unit mass and molecular mass, such as determining the 98 u mass of sulfuric acid or the 84 u mass of sodium hydrogen carbonate. The concept of the mole is a central theme, with questions requiring the conversion of mass into molar quantities (e.g., 180 g of water being 10 moles). The set also reinforces the Law of Conservation of Mass and the distinction between ionic and covalent bonding. By identifying incorrect matches between ions and their valencies, students develop the precision needed for laboratory work and chemical analysis.