Question

An aqueous solution has [C6H5COOH] = 0.110 M and [Ca(C6H5COO)2] = 0.200 M. Ka = 6.3 × 10-5 for C6H5COOH. The solution volume is 5.00 L. What is the pH of the solution after 10.00 mL of 5.00 M NaOH is added? Group of answer choices 4.81 4.86 4.75 4.70 4.65

Answer 1

Answer:

The answer is 4.8659

Explanation:

Given:

[C₆H₅COOH]=0.11M

[C₆H₅COO]=2*0.2=0.4M

Ka=6.3x10⁻⁵

First, calculate the pKa:

$pKa=-logKa=-log(6.3x10^{-5} )=4.2007$

The pH is:

$pH=pKa+log\frac{C6H5COO]}{[C6H5COOH]} =4.2007+log\frac{0.4}{0.11} =4.7614$

Like the volume is 5L, the volume of C₆H₅COO is x, then, the volume of C₆H₅COOH is 5-x

$4.7614=4.2007+log\frac{0.4x}{0.11*(5-x)}$

$0.5607=log\frac{0.4x}{0.11*(5-x)}$

Solving for x:

x=2.49L=2490mL of C₆H₅COO

2510mL of C₆H₅COOH

The milimoles of C₆H₅COOH and C₆H₅COO is:

nC₆H₅COOH=(0.11*2510)-50=226.1mmol

nC₆H₅COO=(0.4*2490)+50=1046mmol

The pH is:

$pH=4.2007+log\frac{1046}{226.1} =4.8659$

Answer 2

Answer:

4.86

Explanation:

The pH of a solution is a measure of the molar concentration of hydrogen ions in the solution and as such is a measure of the acidity or basicity of the solution.

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