Chemistry: Solutions, Acids, and Stoichiometry

• Chemistry topics include solutions, acids and bases, redox reactions, gas laws, and stoichiometry.

Solutions and Their Components

• A solution is a mixture where one substance dissolves into another.
• The substance doing the dissolving is called the solvent.
• The substance being dissolved is the solute.
• Molarity (M) measures the concentration of a solution.
• Molarity is calculated as moles of solute per liter of solution.
• The formula for molarity is M = (moles of solute) / (liters of solution).
• Dilution occurs when water is added to a concentrated solution.
• The formula for dilution is M1V1 = M2V2, where M₁ and V₁ are the molarity and volume of the starting solution, and M₂ and V₂ are the molarity and volume after dilution.

Titrations and Solution Stoichiometry

• Titration is used to determine the concentration of an unknown solution.
• Titration works by reacting the unknown solution with a solution of known concentration.
• An indicator is used to signal when the reaction is complete based on a color change.
• At the equivalence point, the amount of acid and base are equal and the dilution equation (M1V1 = M2V2) can be used.
• Stoichiometry problems with solutions can be solved using the following steps:
  • Convert given information into moles using molarity.
  • Use the balanced equation to find the mole ratio between reactants and products.
  • Convert moles back into the needed units, such as grams or liters.

Electrolytes, Acids, and Bases

• Electrolytes are substances that conduct electricity in water by forming ions.
• Strong electrolytes completely break apart into ions (e.g., NaCl, HCl).
• Weak electrolytes only partially break apart (e.g., acetic acid (CH3COOH)).
• Non-electrolytes do not break apart at all (e.g., sugar, ethanol).
• Acids donate H+ ions.
• Bases donate OH- ions.
• Strong acids completely ionize (e.g., HCl, H2SO4).
• Weak acids partially ionize (e.g., HF, CH3COOH).
• Strong bases completely ionize (e.g., NaOH, KOH).
• Weak bases only partially ionize (e.g., NH3 (ammonia)).

Redox Reactions and Oxidation Numbers

• Oxidation-reduction (redox) reactions involve the transfer of electrons between substances.
• Oxidation is the loss of electrons, which results in the oxidation number increasing.
• Reduction is the gaining of electrons, which results in the oxidation number decreasing.
• OIL RIG: Oxidation Is Loss, Reduction Is Gain.
• Rules for determining oxidation numbers:
  • Elements by themselves have an oxidation number of 0 (e.g., O2, N2, Zn).
  • Group 1 metals have an oxidation number of +1; Group 2 metals are +2.
  • Oxygen usually has an oxidation number of -2, except in peroxides where it is -1.
  • Hydrogen is +1 with nonmetals and -1 with metals.

Balancing Chemical Equations

• Balancing equations ensure the Law of Conservation of Mass is followed.
• To balance an equation, the number of atoms on both sides must be equal.
• Combustion reactions involve hydrocarbons reacting with oxygen to form CO2 and H2O (e.g., CH4 + O2 → CO2 + H2O).
• Balance in the order of C, then H, then O.

Stoichiometry, Limiting Reactants, and Percent Yield

• Stoichiometry deals with the relationships between reactants and products in a balanced chemical equation.
• Limiting reactant problems involve identifying the reactant that runs out first.
• The limiting reactant determines the maximum amount of product that can be made.
• Percent yield compares actual product yield to theoretical yield.
• Percent Yield = (Actual Yield / Theoretical Yield) × 100.

Gas Laws and the Ideal Gas Equation

• Boyle's Law: Pressure and volume are inversely proportional (P1V1 = P2V2).
• Charles' Law: Volume and temperature are directly proportional (V1/T1 = V2/T2).
• Gay-Lussac's Law: Pressure and temperature are directly proportional (P1/T1 = P2/T2).
• Combined Gas Law: Combines Boyle's, Charles', and Gay-Lussac's Laws (P1V1/T1 = P2V2/T2).
• Ideal Gas Law: PV = nRT
  • P = pressure (atm)
  • V = volume (liters)
  • n = moles of gas
  • R = gas constant (0.0821 L-atm/mol·K)
  • T = temperature (Kelvin)
• The Ideal Gas Law can be rearranged to solve for any missing variable.
• When collecting gas over water, subtract water's vapor pressure from the total pressure to find the pressure of the gas.

Explore solutions, acids, bases, redox reactions, gas laws, and stoichiometry. Learn about solution components like solvents and solutes. Understand molarity, dilution, titrations, and solution stoichiometry for accurate chemical analysis.