Find the pH of each mixture of acids. a. 0.075 M in HNO3 and 0.175 M in HC7 H5 O2 b. 0.020 M in

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Find the pH of each mixture of acids. a. 0.075 M in HNO3 and...

Find the $\mathrm{pH}$ of each mixture of acids. a. 0.075 $\mathrm{M}$ in $\mathrm{HNO}_{3}$ and 0.175 $\mathrm{M}$ in $\mathrm{HC}_{7} \mathrm{H}_{5} \mathrm{O}_{2}$ b. 0.020 $\mathrm{M}$ in $\mathrm{HBr}$ and 0.015 $\mathrm{M} \mathrm{in} \mathrm{HClO}_{4}$ c. 0.095 $\mathrm{M}$ in $\mathrm{HF}$ and 0.225 $\mathrm{M}$ in $\mathrm{HC}_{6} \mathrm{H}_{5} \mathrm{O}$ d. 0.100 $\mathrm{M}$ in formic acid and 0.050 $\mathrm{M}$ in hypochlorous acid

Find the $\mathrm{pH}$ of each mixture of acids.
a. 0.075 $\mathrm{M}$ in $\mathrm{HNO}_{3}$ and 0.175 $\mathrm{M}$ in $\mathrm{HC}_{7} \mathrm{H}_{5} \mathrm{O}_{2}$
b. 0.020 $\mathrm{M}$ in $\mathrm{HBr}$ and 0.015 $\mathrm{M} \mathrm{in} \mathrm{HClO}_{4}$
c. 0.095 $\mathrm{M}$ in $\mathrm{HF}$ and 0.225 $\mathrm{M}$ in $\mathrm{HC}_{6} \mathrm{H}_{5} \mathrm{O}$
d. 0.100 $\mathrm{M}$ in formic acid and 0.050 $\mathrm{M}$ in hypochlorous acid

Key Concepts

pH is a measure of the acidity or basicity of a solution, defined as the negative logarithm (base 10) of the hydrogen ion concentration. It is a central concept in acid–base chemistry and allows chemists to quantify how acidic or basic a solution is.

Strong Acids vs Weak Acids

Acids are categorized based on their degree of dissociation in water. Strong acids, such as nitric acid, HBr, and HClO4, dissociate completely in solution, providing a reliable and predictable concentration of hydrogen ions. In contrast, weak acids, such as HF, formic acid, and hypochlorous acid, only partially dissociate, meaning that an equilibrium is established between the undissociated acid and its ions. Understanding this distinction is crucial when determining the pH of acidic mixtures.

Acid Dissociation Equilibrium and Ka

For weak acids, the dissociation equilibrium is given by the expression Ka = [H+][A-]/[HA], where Ka is the acid dissociation constant. The value of Ka indicates how readily a weak acid donates protons in solution. This concept is essential when calculating the contribution of weak acids to the overall hydrogen ion concentration in the solution.

Additivity and Dominance in Acid Mixtures

When multiple acids are present in a solution, the acid that dissociates more completely (or has a larger effective contribution of hydrogen ions) will primarily determine the solution's pH. In mixtures containing both strong and weak acids, the hydrogen ion concentration from the strong acid typically dominates the pH calculation. Understanding the relative contributions of each acid based on their dissociation helps simplify and accurately compute the overall pH.

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