Study Notes
Stoichiometry involves understanding the relationships between the quantities of reactants and products in chemical reactions. It includes concepts like the mole, reacting masses and volumes, and the ideal gas equation.
- Element — a substance made from one kind of atom Example: Sodium (Na)
- Compound — a substance made from two or more elements chemically combined Example: Sodium chloride (NaCl)
- Mixture — a combination of two or more substances that are not chemically combined Example: Air
- Mole — a unit that measures the amount of substance, equivalent to Avogadro's number of particles Example: 1 mole of carbon-12 weighs 12 grams
- Limiting Reactant — the reactant that is completely consumed in a reaction, limiting the amount of product formed Example: In the reaction of hydrogen and oxygen to form water, if hydrogen is in excess, oxygen is the limiting reactant
- Ideal Gas Equation — an equation that relates the pressure, volume, temperature, and number of moles of a gas Example: PV = nRT
Exam Tips
Key Definitions to Remember
- Element: A substance made from one kind of atom
- Compound: A substance made from two or more elements chemically combined
- Mole: A unit that measures the amount of substance
Common Confusions
- Confusing mixtures with compounds
- Misunderstanding the concept of limiting reactants
Typical Exam Questions
- What is a mole? A mole is a unit that measures the amount of substance, equivalent to Avogadro's number of particles.
- How do you determine the limiting reactant in a reaction? Calculate the moles of each reactant and compare them to the stoichiometric ratios in the balanced equation.
- What is the ideal gas equation? PV = nRT, where P is pressure, V is volume, n is moles, R is the gas constant, and T is temperature.
What Examiners Usually Test
- Understanding of the mole concept and calculations
- Ability to balance chemical equations
- Application of the ideal gas equation