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Chemistry guides

12 articles

Chemistry5 min read
Molecular Weight: Add Up the Atoms, Step by Step
Molecular weight is the sum of atomic masses in a formula: H₂O is 2 × 1.008 + 15.999 = 18.015 g/mol. Learn the method, brackets and hydrates included.
Chemistry5 min read
Convert Moles to Grams (and Back Again)
Grams = moles × molar mass: 2 mol of water at 18.015 g/mol weighs 36.03 g. Learn the two-way conversion with a gas-free worked example and a tip on purity.
Chemistry4 min read
Reaction Conversion: What Fraction of the Feed Reacted?
Conversion = reactant consumed ÷ fed × 100. If 117 of 150 mol/h reacts, conversion is 78%; yield and selectivity tell the rest of the story.
Chemistry4 min read
Percent Excess Reactant: Formula, Steps and a Worked Case
Percent excess = (fed − required) ÷ required × 100. Feeding 6 mol of N₂ where 5 mol is needed means a 20% excess; the steps tell you which species to use.
Chemistry4 min read
Mass Percent of a Solution: Solute ÷ Solution × 100
Dissolving 15 g of solute in a total of 300 g of solution gives 5% w/w. See the formula, how to prepare a batch and the classic denominator mistake.
Chemistry4 min read
Normality of a Solution: N = M × Equivalents Per Mole
Normality is molarity times the equivalents each mole supplies, so 0.25 M sulfuric acid is 0.50 N in an acid–base reaction. Here is the rule and a titration.