Table of contents

1. Intro to General Chemistry3h 48m
2. Atoms & Elements4h 16m
3. Chemical Reactions4h 10m
4. BONUS: Lab Techniques and Procedures1h 36m
5. BONUS: Mathematical Operations and Functions48m
6. Chemical Quantities & Aqueous Reactions3h 53m
7. Gases3h 49m
8. Thermochemistry2h 37m
9. Quantum Mechanics2h 58m
10. Periodic Properties of the Elements3h 9m
11. Bonding & Molecular Structure3h 29m
12. Molecular Shapes & Valence Bond Theory1h 57m
13. Liquids, Solids & Intermolecular Forces2h 23m
14. Solutions3h 1m
15. Chemical Kinetics2h 53m
16. Chemical Equilibrium2h 29m
17. Acid and Base Equilibrium5h 1m
18. Aqueous Equilibrium4h 47m
19. Chemical Thermodynamics1h 50m
20. Electrochemistry2h 42m
21. Nuclear Chemistry2h 36m
22. Organic Chemistry5h 7m
23. Chemistry of the Nonmetals2h 39m
24. Transition Metals and Coordination Compounds3h 16m

18. Aqueous Equilibrium

Acid-Base Indicators

General Chemistry

18. Aqueous Equilibrium

Acid-Base Indicators

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Multiple Choice

Consider the titration of 26.00 mL of 0.400 M formic acid with 0.380 M NaOH. Calculate the pH of the solution at the half-equivalence point.

3.75

4.25

2.50

5.00

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Verified step by step guidance

Identify the concept of the half-equivalence point in a titration. At this point, half of the acid has been neutralized by the base, and the concentration of the acid is equal to the concentration of its conjugate base.

Recognize that formic acid (HCOOH) is a weak acid, and its dissociation in water can be represented by the equation:

{H COOH}_{(aq)} \leftrightarrow {H COO}_{-} (aq) + H_{+} (aq)

At the half-equivalence point, the pH of the solution is equal to the pKa of the acid. Use the formula:

pH = pKa

. Look up the pKa value for formic acid, which is approximately 3.75.

Calculate the moles of formic acid initially present using the formula:

moles = volume \times molarity

. Substitute the given values:

26.00 mL \times 0.400 M

Understand that at the half-equivalence point, the amount of NaOH added is half the initial moles of formic acid. This means the concentrations of formic acid and its conjugate base are equal, confirming that the pH is equal to the pKa.