General Chemistry Review Chapters 16-20

Buffer Solutions

• A solution comprising equal amounts of HNO2 (weak acid) and NaNO2 (conjugate base) will resist pH changes, showcasing its buffering capacity.
• The combination of HF (weak acid) and KF (its salt) generates a buffer system.

pH Calculations

• A buffer solution of 0.500 M HF and 0.300 M NaF produces a pH of 3.24.
• Adding 0.100 moles of NaOH to 0.250 moles of HF results in a pH of 3.28.
• To achieve a pH of 4.95 with 0.450 moles of HC2H3O2, 59.9 g of NaC2H3O2 is required.
• After adding 2.5 g of KOH to a buffer of 0.400 M HF and 0.250 M LiF, the pH rises to 3.37.

Titration Insights

• The addition of 15.0 g of HCl can neutralize a buffer solution of 0.50 M HC2H3O2 and 0.40 M NaC2H3O2, effectively destroying its buffering ability.
• In titrations involving weak acids and strong bases, the pH at the equivalence point is always greater than 7, indicating a basic environment.
• Calculating the titration of 25.0 mL of 0.650 M HF with 0.500 M NaOH requires 32.5 mL of NaOH to reach the equivalence point.
• For the titration of 30.0 mL of 0.850 M NH3 with 0.100 M HCl, the initial pH is notably basic at 11.60.

pH During Titration

• The pH after 15.0 mL of 0.350 M KOH is added to 20.0 mL of 0.500 M HC2H3O2 is measured at 4.79.
• At the equivalence point for the same titration, the pH is recorded at 9.01.
• Adding 5.00 mL of excess KOH post-equivalence in the same titration raises the pH to 12.51.

Solubility Products

• The molar solubility of PbBr2 in pure water is derived from its Ksp of 4.67 × 10−6, yielding a solubility of 1.05 × 10−2 M.
• CaCO3 displayed a molar solubility of 9.92 × 10−9 M when in a solution with 0.500 M Na2CO3.

Spontaneous Processes and Entropy

• Processes considered spontaneous include a ball rolling down a hill and the rusting of a car.
• An entropy calculation shows that a system with 2.50 × 10^8 arrangements has an entropy of 2.67 × 10^-22 J/K.
• A positive ΔSsystem alone cannot determine overall process spontaneity; ΔSuniverse must be analyzed.

Changes in Entropy

• The formation of ice from water at −25 °C would have a negative ΔS, indicating reduced disorder compared to the liquid state.

This quiz focuses on fundamental concepts from General Chemistry, specifically covering chapters 16 to 20. You will explore various chemical principles, including properties of solutions and acid-base reactions. Test your knowledge with these flashcards designed for review and consolidation of key ideas.