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4. Find the pH at each of the following points in the titration of 25 mL of 0.3 M HF with 0.3 M NaOH. The Ka value is 6.6x10-4 a. The initial pH b. After adding 10mL of 0.3 M NaOH c. After adding 12.5 mL of 0.3 M NaOH d. After adding 25 mL of 0.3 M NaOH e. After adding 26 mL of 0.3 M NaOH

Answer :

Walexis

Explanation:

Since HF is a weak acid, the use of an ICE table is required to find the pH. The question gives us the concentration of the HF.

HF+H2O⇌H3O++F−HF+H2O⇌H3O++F−

Initial0.3 M-0 M0 MChange- X-+ X+XEquilibrium0.3 - X-X MX M

Writing the information from the ICE Table in Equation form yields

6.6×10−4=x20.3−x6.6×10−4=x20.3−x

Manipulating the equation to get everything on one side yields

0=x2+6.6×10−4x−1.98×10−40=x2+6.6×10−4x−1.98×10−4

Now this information is plugged into the quadratic formula to give

x=−6.6×10−4±(6.6×10−4)2−4(1)(−1.98×10−4)−−−−−−−−−−−−−−−−−−−−−−−−−−−−√2x=−6.6×10−4±(6.6×10−4)2−4(1)(−1.98×10−4)2

The quadratic formula yields that x=0.013745 and x=-0.014405

However we can rule out x=-0.014405 because there cannot be negative concentrations. Therefore to get the pH we plug the concentration of H3O+ into the equation pH=-log(0.013745) and get pH=1.86

When the pH we plug the concentration of H3O+ into the equation pH is =-log(0.013745) and also get pH=1.86

What is the Weak Acid?

When the HF is a weak acid, Then the use of an ICE table is required to find the pH. The question that gives us the concentration of the HF is:

HF+H2O⇌H3O++F−HF+H2O⇌H3O++F−

Now, The Initial0.3 M-0 M0 MChange- X-+ X+XEquilibrium0.3 - X-X MX M

After that, Writing the information from the ICE Table in Equation form yields

Then, 6.6×10−4=x20.3−x6.6×10−4=x20.3−x

Now, Manipulating the equation to get everything on one side yields

Also, 0 is =x2+6.6×10−4x−1.98×10−40=x2+6.6×10−4x−1.98×10−4

Now this the information is plugged into the quadratic formula to give

Then x=−6.6×10−4±(6.6×10−4)2−4(1)(−1.98×10−4)−−−−−−−−−−−−−−−−−−−−−−−−−−−−√2x is =−6.6×10−4±(6.6×10−4)2−4(1)(−1.98×10−4)2

Then The quadratic formula yields that x=0.013745 and also x is =-0.014405

However, when we can rule out x is =-0.014405 because there can't be negative concentrations.

Thus to get the pH we plug the concentration of H3O+ into the equation pH is =-log(0.013745) and also get pH=1.86

Find more information about Weak Acid here:

https://brainly.com/question/27135494

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