01Separate the formula from the coefficient
A subscript is part of a substance’s chemical formula. A coefficient tells you how many formula units or molecules participate in the represented reaction. Changing H₂O to H₂O₂ changes the substance; changing H₂O to 2H₂O changes its amount. Before balancing or calculating, read each formula carefully and count every element. Parentheses and subscripts apply together, so Ca(OH)₂ contains two oxygen atoms and two hydrogen atoms per formula unit.
02Track the meaning of each quantity
Mass, amount of substance, concentration, and volume describe different things. Write units alongside every value and identify the conversion that connects them. A balanced reaction gives mole ratios between substances; it does not directly give equal mass ratios. When reviewing Solvi’s explanation, ask which relationship justifies each conversion. Keeping this chain visible can reveal a mistaken factor even when the arithmetic itself is correct.
03Check conservation and chemical context
Count atoms on both sides of a balanced equation, and check total charge when working with ionic equations. For a calculation, ask whether the available reactants limit the amount of product. Use the conditions supplied by your course: state symbols, reaction conditions, or solution concentration may matter. Study explanations are for understanding coursework; follow your teacher’s and laboratory’s instructions for any practical experiment instead of treating a homework response as an experimental procedure.