Henderson-Hasselbalch Equation - AP Chemistry
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How does dilution affect the pH of a buffer according to the Henderson-Hasselbalch equation?
How does dilution affect the pH of a buffer according to the Henderson-Hasselbalch equation?
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pH remains relatively constant. Ratio stays constant when both components dilute equally.
pH remains relatively constant. Ratio stays constant when both components dilute equally.
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What happens to pH if $[A^-] = [HA]$ in the Henderson-Hasselbalch equation?
What happens to pH if $[A^-] = [HA]$ in the Henderson-Hasselbalch equation?
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pH equals $pK_a$. When the ratio equals 1, the log term becomes zero.
pH equals $pK_a$. When the ratio equals 1, the log term becomes zero.
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What assumption is made about $[A^-]$ and $[HA]$ in the Henderson-Hasselbalch equation?
What assumption is made about $[A^-]$ and $[HA]$ in the Henderson-Hasselbalch equation?
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They are equilibrium concentrations. Assumes no significant change from initial values.
They are equilibrium concentrations. Assumes no significant change from initial values.
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What does the term 'buffer capacity' refer to?
What does the term 'buffer capacity' refer to?
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The amount of acid or base the buffer can neutralize. Measures resistance to pH change upon acid/base addition.
The amount of acid or base the buffer can neutralize. Measures resistance to pH change upon acid/base addition.
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What is the primary use of the Henderson-Hasselbalch equation?
What is the primary use of the Henderson-Hasselbalch equation?
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To calculate the pH of buffer solutions. Combines weak acid-base pairs to resist pH changes.
To calculate the pH of buffer solutions. Combines weak acid-base pairs to resist pH changes.
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Identify the meaning of $[A^-]$ in the Henderson-Hasselbalch equation.
Identify the meaning of $[A^-]$ in the Henderson-Hasselbalch equation.
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The concentration of the conjugate base. The deprotonated form of the weak acid.
The concentration of the conjugate base. The deprotonated form of the weak acid.
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What is the effect of temperature on $pK_a$ in the Henderson-Hasselbalch equation?
What is the effect of temperature on $pK_a$ in the Henderson-Hasselbalch equation?
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$pK_a$ can change with temperature. Temperature affects equilibrium constant values.
$pK_a$ can change with temperature. Temperature affects equilibrium constant values.
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If $[HA] = 0.1$ M and $[A^-] = 0.01$ M, how does pH compare to $pK_a$?
If $[HA] = 0.1$ M and $[A^-] = 0.01$ M, how does pH compare to $pK_a$?
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pH < $pK_a$. More acid than base means pH below $pK_a$.
pH < $pK_a$. More acid than base means pH below $pK_a$.
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How does the Henderson-Hasselbalch equation relate to buffers?
How does the Henderson-Hasselbalch equation relate to buffers?
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It calculates the pH of a buffer given $pK_a$, $[A^-]$, and $[HA]$. Uses component concentrations to predict buffer pH.
It calculates the pH of a buffer given $pK_a$, $[A^-]$, and $[HA]$. Uses component concentrations to predict buffer pH.
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For a buffer with $pK_a = 6.3$, what is pH when $[A^-] = 0.5$ M, $[HA] = 0.25$ M?
For a buffer with $pK_a = 6.3$, what is pH when $[A^-] = 0.5$ M, $[HA] = 0.25$ M?
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pH = 6.6. $\text{log}(2) = 0.3$, so pH = 6.3 + 0.3.
pH = 6.6. $\text{log}(2) = 0.3$, so pH = 6.3 + 0.3.
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Identify the meaning of $[HA]$ in the Henderson-Hasselbalch equation.
Identify the meaning of $[HA]$ in the Henderson-Hasselbalch equation.
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The concentration of the weak acid. The protonated form that can donate hydrogen ions.
The concentration of the weak acid. The protonated form that can donate hydrogen ions.
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In the Henderson-Hasselbalch equation, what does a higher $pK_a$ indicate?
In the Henderson-Hasselbalch equation, what does a higher $pK_a$ indicate?
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A weaker acid. Larger $pK_a$ corresponds to smaller $K_a$ value.
A weaker acid. Larger $pK_a$ corresponds to smaller $K_a$ value.
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Calculate pH if $pK_a = 9.3$, $[A^-] = 0.05$ M, $[HA] = 0.1$ M.
Calculate pH if $pK_a = 9.3$, $[A^-] = 0.05$ M, $[HA] = 0.1$ M.
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pH = 9.0. $\text{log}(0.5) = -0.3$, so pH = 9.3 - 0.3.
pH = 9.0. $\text{log}(0.5) = -0.3$, so pH = 9.3 - 0.3.
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What is the logarithmic form of the Henderson-Hasselbalch equation?
What is the logarithmic form of the Henderson-Hasselbalch equation?
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$pH = pK_a + \text{log}(\frac{[A^-]}{[HA]})$. Standard form using base-10 logarithm.
$pH = pK_a + \text{log}(\frac{[A^-]}{[HA]})$. Standard form using base-10 logarithm.
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What is the relation between pH and $pK_a$ when pH > $pK_a$?
What is the relation between pH and $pK_a$ when pH > $pK_a$?
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The solution has more conjugate base than acid. Higher pH indicates more base than acid present.
The solution has more conjugate base than acid. Higher pH indicates more base than acid present.
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What does the Henderson-Hasselbalch equation assume about ionic strength?
What does the Henderson-Hasselbalch equation assume about ionic strength?
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It is constant. Simplifies calculations by ignoring activity coefficients.
It is constant. Simplifies calculations by ignoring activity coefficients.
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Determine the pH if $pK_a = 7.8$, $[A^-] = 0.3$ M, $[HA] = 0.1$ M.
Determine the pH if $pK_a = 7.8$, $[A^-] = 0.3$ M, $[HA] = 0.1$ M.
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pH = 8.3. $\text{log}(3) ≈ 0.5$, so pH = 7.8 + 0.5.
pH = 8.3. $\text{log}(3) ≈ 0.5$, so pH = 7.8 + 0.5.
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Which condition is assumed in the Henderson-Hasselbalch equation?
Which condition is assumed in the Henderson-Hasselbalch equation?
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The solution is a buffer solution. Contains both weak acid and conjugate base in equilibrium.
The solution is a buffer solution. Contains both weak acid and conjugate base in equilibrium.
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What is the impact on pH if $[A^-]$ decreases in the buffer solution?
What is the impact on pH if $[A^-]$ decreases in the buffer solution?
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pH decreases. Less conjugate base shifts equilibrium toward lower pH.
pH decreases. Less conjugate base shifts equilibrium toward lower pH.
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What is the effect on pH if $[A^-]$ increases relative to $[HA]$?
What is the effect on pH if $[A^-]$ increases relative to $[HA]$?
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pH increases. Larger numerator in ratio increases log term value.
pH increases. Larger numerator in ratio increases log term value.
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Find the pH if $pK_a = 4.75$, $[A^-] = 0.1$ M, $[HA] = 0.1$ M.
Find the pH if $pK_a = 4.75$, $[A^-] = 0.1$ M, $[HA] = 0.1$ M.
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pH = 4.75. Equal concentrations make the log term zero.
pH = 4.75. Equal concentrations make the log term zero.
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For a buffer with $pK_a = 4.5$, what is pH when $[A^-] = 0.2$ M and $[HA] = 0.1$ M?
For a buffer with $pK_a = 4.5$, what is pH when $[A^-] = 0.2$ M and $[HA] = 0.1$ M?
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pH = 4.8. $\text{log}(2) = 0.3$, so pH = 4.5 + 0.3.
pH = 4.8. $\text{log}(2) = 0.3$, so pH = 4.5 + 0.3.
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Calculate the pH if $pK_a = 5.4$, $[A^-] = 0.2$ M, $[HA] = 0.2$ M.
Calculate the pH if $pK_a = 5.4$, $[A^-] = 0.2$ M, $[HA] = 0.2$ M.
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pH = 5.4. Equal concentrations make the log term zero.
pH = 5.4. Equal concentrations make the log term zero.
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State the formula for the Henderson-Hasselbalch equation.
State the formula for the Henderson-Hasselbalch equation.
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$pH = pK_a + \text{log}(\frac{[A^-]}{[HA]})$. Relates buffer pH to acid strength and component ratio.
$pH = pK_a + \text{log}(\frac{[A^-]}{[HA]})$. Relates buffer pH to acid strength and component ratio.
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What does the ratio $[A^-]/[HA]$ signify in the Henderson-Hasselbalch equation?
What does the ratio $[A^-]/[HA]$ signify in the Henderson-Hasselbalch equation?
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Relative amounts of conjugate base and weak acid. Determines whether solution is acidic or basic.
Relative amounts of conjugate base and weak acid. Determines whether solution is acidic or basic.
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State the logarithmic property used in the Henderson-Hasselbalch equation.
State the logarithmic property used in the Henderson-Hasselbalch equation.
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$\text{log}(a/b) = \text{log}(a) - \text{log}(b)$. Allows separation of the concentration ratio term.
$\text{log}(a/b) = \text{log}(a) - \text{log}(b)$. Allows separation of the concentration ratio term.
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What does $pK_a$ represent in the Henderson-Hasselbalch equation?
What does $pK_a$ represent in the Henderson-Hasselbalch equation?
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The negative logarithm of the acid dissociation constant. Higher $pK_a$ means weaker acid dissociation.
The negative logarithm of the acid dissociation constant. Higher $pK_a$ means weaker acid dissociation.
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Find the pH if $pK_a = 8.0$, $[A^-] = 0.1$ M, $[HA] = 0.05$ M.
Find the pH if $pK_a = 8.0$, $[A^-] = 0.1$ M, $[HA] = 0.05$ M.
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pH = 8.3. $\text{log}(2) = 0.3$, so pH = 8.0 + 0.3.
pH = 8.3. $\text{log}(2) = 0.3$, so pH = 8.0 + 0.3.
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What is the relation between pH and $pK_a$ when pH < $pK_a$?
What is the relation between pH and $pK_a$ when pH < $pK_a$?
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The solution has more weak acid than conjugate base. Lower pH indicates more acid than base present.
The solution has more weak acid than conjugate base. Lower pH indicates more acid than base present.
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How is the Henderson-Hasselbalch equation used in biological systems?
How is the Henderson-Hasselbalch equation used in biological systems?
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To maintain pH in physiological systems. Blood pH regulation uses bicarbonate buffer system.
To maintain pH in physiological systems. Blood pH regulation uses bicarbonate buffer system.
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