4. Chemical Reactions Flashcards
What Are Chemical Equations?
Expressions that describe chemical reactions.
Show changes in state of matter or compound formation.
What Are Reactants & Products?
Reactants: Substances on the left side of the equation.
Products: Substances on the right side of the equation.
What Are Coefficients & Subscripts?
Coefficients: Numbers before a compound, indicating the amount.
Subscripts: Small numbers within a formula, showing the number of atoms in a molecule.
How Are States of Matter Shown?
(g) = Gas
(l) = Liquid
(s) = Solid
What Is a Balanced Chemical Equation?
Same number of each element on both sides.
Maintains the law of conservation of mass.
How to Balance a Chemical Equation?
- Identify elements in reactants & products.
- Adjust coefficients to balance atoms on both sides.
- Start with elements that appear in only one reactant & product.
- Keep coefficients small & simple.
- Do not change subscripts (would alter the compound’s identity).
Why Use Moles in Balancing?
Avogadro’s number allows equations to be scaled.
1 mole of reactants reacts with proportional moles of products.
What is stoichiometry?
The study of quantities in chemical reactions, using balanced equations to determine the amount of reactants and products.
What are stoichiometric proportions?
The mole ratios of reactants and products in a balanced chemical equation.
How do you convert moles to grams?
Multiply the number of moles by the molar mass of the substance.
What is the limiting reagent?
The reactant that runs out first, stopping the reaction.
Why is the most expensive reactant usually the limiting reagent in industrial chemistry?
To minimize waste and maximize cost efficiency.
What is theoretical yield?
The maximum possible amount of product that can be obtained.
What factors reduce actual yield?
Side reactions, reversible reactions, recovery issues, energy losses, and heterogeneous conditions.
What is the First Law of Thermodynamics?
Energy cannot be created or destroyed, only converted between forms.
What is enthalpy?
The heat exchanged at constant pressure.
What is the difference between an open, closed, and isolated system?
Open: Exchanges mass and energy with surroundings.
Closed: Exchanges energy but not mass.
Isolated: No exchange of mass or energy.
What is an exothermic vs. endothermic reaction?
Exothermic: Releases heat (negative enthalpy).
Endothermic: Absorbs heat (positive enthalpy).
What is chemical equilibrium?
A state where the forward and reverse reaction rates are equal.
What is the equilibrium constant (K)?
A ratio that determines the direction of a reaction at equilibrium.
How does Le Châtelier’s Principle explain shifts in equilibrium?
More reactant added: Shifts toward products.
Increase in pressure: Shifts toward fewer gas molecules.
Increase in temperature: Shifts to absorb excess heat.
What is the Arrhenius equation used for?
Describes the temperature dependence of reaction rates.
What is a catalyst?
A substance that speeds up a reaction without being consumed.
How do catalysts work?
They lower activation energy, increasing the reaction rate.
