Misconceptions

#	✗ Wrong Belief	✓ Correct Understanding
1	"1 mol always weighs 1 g"	1 mol weighs molar mass grams. $H_{2}$ = 2 g/mol; NaCl = 58.5 g/mol.
2	"22.4 L is the volume of 1 mol of any gas at any temperature"	22.4 L/mol applies only at STP (0 °C, 1 atm). At 25 °C it is ~24.5 L/mol.
3	"The empirical formula always differs from the molecular formula"	They can be identical — e.g., $H_{2}$ O, $CO_{2}$ , NaCl all have empirical = molecular formula.
4	"Limiting reagent is always the reactant present in smaller mass"	Limiting reagent is determined by mole ratio relative to stoichiometry, not by mass alone.
5	"Molarity and molality are the same at room temperature"	They are different: M uses volume of solution; m uses mass of solvent. They are numerically similar only in very dilute aqueous solutions.
6	"Normality is always twice the molarity"	Normality = Molarity × n-factor. n-factor depends on the specific reaction — it is 1 for HCl, 2 for $H_{2}$$SO_{4}$ in neutralisation, but different in other reactions.
7	"Mole fraction can be greater than 1"	Mole fraction is always between 0 and 1. Sum of mole fractions of all components = 1.
8	"% composition and mole fraction are the same thing"	% composition is by mass; mole fraction is by moles. Converting requires dividing by molar mass.
9	"Avogadro's number is $6.023 \times 10^{23}$ "	The correct value is $6.022 \times 10^{23}$ $mol^{-1}$ (CODATA 2018: $6.02214076 \times 10^{23}$ ).
10	"When a question says 'at STP', you can use PV = nRT freely"	Use PV = nRT only when T and P are explicitly given. At stated STP (0 °C, 1 atm), use 22.4 L/mol directly for speed.