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1. Intro to General Chemistry3h 48m
2. Atoms & Elements4h 16m
3. Chemical Reactions4h 10m
4. BONUS: Lab Techniques and Procedures1h 38m
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

Henderson-Hasselbalch Equation

General Chemistry

18. Aqueous Equilibrium

Henderson-Hasselbalch Equation

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Multiple Choice

What mass of KNO2 must be added to create 200.0 mL of a buffer solution with a pH of 3.00 and an HNO2 concentration of 0.150 M? The pKₐ of nitrous acid is 3.34.

0.024 g

0.012 g

0.096 g

0.048 g

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Verified step by step guidance

First, understand that a buffer solution consists of a weak acid and its conjugate base. In this case, HNO2 is the weak acid and KNO2 provides the conjugate base NO2⁻.

Use the Henderson-Hasselbalch equation to relate the pH of the buffer solution to the concentrations of the acid and its conjugate base:

p_{H} = p_{K} + log (\frac{[A_{-]}}{[{HA}_{]}})

, where

p_{K}

is the acid dissociation constant,

[{HA}_{]}

is the concentration of the acid, and

[A_{-]}

is the concentration of the conjugate base.

Rearrange the Henderson-Hasselbalch equation to solve for the concentration of the conjugate base NO2⁻:

[A_{-]} = [{HA}_{] \times 10^{p_{H} - p_{K}}}

Substitute the given values into the equation:

[A_{-]} = 0.150 \times 10^{3.00 - 3.34}

. Calculate the concentration of NO2⁻.

Convert the concentration of NO2⁻ to mass using the molar mass of KNO2. First, calculate the moles of NO2⁻ in 200.0 mL of solution, then use the molar mass of KNO2 to find the mass: