Passage 1 — Mole Concept

The mole is the SI unit for amount of substance. One mole of any substance contains exactly (1) entities. This number is called (2). The mass of one mole of a substance in grams is called its (3) and numerically equals the (4) in atomic mass units. At STP (0 °C, 1 atm), one mole of an ideal gas occupies (5) litres — called the (6).

Passage 2 — Concentration Terms

Molarity is defined as moles of solute per (7) of solution, while molality is defined as moles of solute per (8) of solvent. The key difference is that molarity is (9)-dependent whereas molality is (10)-independent. The formula to convert mass % to molarity is M = (1000 × d × w%) ÷ ((11) × 100). The sum of all mole fractions in a mixture always equals (12).

Passage 3 — Stoichiometry

When reactants are not present in stoichiometric proportions, the reactant that is consumed first is called the (13). It determines the (14) of the reaction. The empirical formula gives the (15) ratio of atoms, while the molecular formula gives the (16) number of atoms. The relationship between them is: molecular formula = (17) × empirical formula, where the multiplier equals (18) divided by empirical formula mass.