Study guides › C/P › General Chemistry

Stoichiometry & Chemical Reactions

Stoichiometry is the bookkeeping of chemistry. You will convert between grams, moles, and particles, balance equations, find limiting reagents and yields, assign oxidation states, and link all of it to solution concentrations and titrations.

Study this chapter in PrepMed (free)

What this chapter covers

• The Mole, Molar Mass & Formulas. Nearly every general chemistry calculation starts by converting grams to moles, and formula questions reuse the same steps.
• Balancing Equations & Reaction Types. You must balance a reaction before any mole-ratio question is possible, and recognizing the reaction type tells you what the products are.
• Limiting Reagents & Percent Yield. Yield questions almost always hide a limiting reagent, so learn to find it first and then calculate from it.
• Oxidation States & Redox Reactions. Tracking electrons through oxidation numbers is the foundation for electrochemistry, biochemistry, and organic oxidations.
• Concentration & Solution Stoichiometry. Molarity ties moles to volume, so titration and dilution questions are just mole-ratio problems in disguise.

Key points to know

• 1 mol = 6.022 × 10²³ particles; molar mass in g/mol equals atomic mass in amu
• Moles = grams ÷ molar mass
• Balance with coefficients only, never subscripts
• Leave elements found as free O₂ or H₂ until last
• Limiting reagent gives the smallest (moles ÷ coefficient)
• Theoretical yield is always calculated from the limiting reagent
• Oxidation = loss of e⁻ (number goes up); reduction = gain (number goes down)
• Oxidizing agent is reduced; reducing agent is oxidized

Try a practice question

How many moles are in 88 g of CO₂ (M = 44 g/mol)?

1. 0.5 mol
2. 1 mol
3. 2 mol
4. 4 mol

Common questions

24 original practice questions accompany this chapter in the app. Spaced review brings missed ideas back at the right time; it helps memory but cannot promise you will not miss an idea again.