Concentration and pH Caculation of Titrations

In summary, you calculated the volume of 0.116 M HCl(aq) needed to neutralize 25.0 mL of 0.215 M KOH(aq) and determined the molarity of Cl- ions at the stoichiometric point to be 0.0754 M. You also correctly calculated the pH of the solution after adding 40.0 mL of 0.116 M HCl(aq) to 25.0 mL of 0.215 M KOH(aq), obtaining a pH of 12.0533.
  • #1
Squall
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Homework Statement



Calculate the volume of 0.116 M HCl(aq) required to neutralize the following solutions.
all the hydroxide ions in 25.0 mL of 0.215 M KOH(aq)

1. What is the molarity of Cl - ions at the stoichiometric point?


Homework Equations



HCl + KOH --> KCl + H2O

The Attempt at a Solution



1. So I am running out of ideas and need some help please take a look.

so at the stoichiometric point the amount of acid and base moles are equal
so .215M*.025L=.005375 moles of base that needs to be neutralized
so .005375n/.116M=.0463L

My theory is that the amount of Cl- ion in the solution is equal to the amount of moles of acid used since KCl is formed in the reaction and KCl dissociates into K+ and Cl- ions completely.

So then the molarity of Cl- at the stoichiometric point is
.005375 moles/(.0463L + .025L)=.0754M


2. Calculate the pH of the solution after the addition of 40.0 mL of 0.116 M HCl(aq) to 25.0 mL of 0.215 M KOH(aq).

.04L*.116M=.00464moles
.025L*.215M=.005375moles

so we subtract .005375n-.00464n=0.000735 moles of KOH left
no we get concentration by dividing .000735moles/(.04+.025)L=.01131 Molar
to get pH we first calculate the pOH since we still have base present
-log(.01131)=1.9466
pH= 14 - 1.9466 = 12.0533
I don't understand why this is the wrong answer seems like I did all the other problems the same way and got a right answer, but here I don't get it. If you guys can please take a look and see if I am missing something I would greatly appreciate your help.
Than You
 
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  • #2
You are doing great and these are correct answers.
 

FAQ: Concentration and pH Caculation of Titrations

What is concentration and pH calculation of titrations?

Concentration and pH calculation of titrations is the process of determining the concentration of a solution or the pH of a solution using titration. Titration is a technique in which a known concentration of a solution is added to a solution of unknown concentration until a reaction is complete. By knowing the volume and concentration of the added solution, the concentration or pH of the unknown solution can be calculated.

What is the purpose of concentration and pH calculation of titrations?

The purpose of concentration and pH calculation of titrations is to determine the concentration or pH of a solution. This information is important in many scientific fields, such as chemistry, biology, and environmental science. It can be used to determine the purity of a substance, the strength of an acid or base, and the effectiveness of a chemical reaction.

What are the steps involved in concentration and pH calculation of titrations?

The steps involved in concentration and pH calculation of titrations include:
1. Preparing the solutions: This involves accurately measuring the volumes of the solutions and their concentrations.
2. Performing the titration: The known solution is added to the unknown solution until a reaction is complete.
3. Recording the volume of the added solution: This is used to calculate the concentration or pH of the unknown solution.
4. Calculating the concentration or pH: This is done using the volume and concentration of the added solution, as well as any other relevant equations or data.
5. Repeating the titration: It is important to repeat the titration multiple times to ensure accuracy and precision in the results.

What are some factors that can affect the accuracy of concentration and pH calculation of titrations?

Some factors that can affect the accuracy of concentration and pH calculation of titrations include:
1. Human error: Accurately measuring the volumes and concentrations of the solutions is crucial for accurate results.
2. Presence of impurities: Impurities in the solutions can affect the reaction and lead to inaccurate results.
3. Temperature: Changes in temperature can affect the volume of the solutions and therefore impact the accuracy of the results.
4. Incorrect calibration of equipment: It is important to regularly calibrate equipment such as burettes and pH meters to ensure accurate measurements.
5. Incomplete reaction: If the reaction is not allowed to fully complete, the results will be inaccurate.

What are some common applications of concentration and pH calculation of titrations?

Concentration and pH calculation of titrations have many applications in various fields. Some common examples include:
1. Testing the purity of a substance: By determining the concentration of a solution, the purity of a substance can be determined.
2. Analyzing acid or base strength: Titration can be used to determine the strength of an acid or base, which is important in industrial processes and environmental studies.
3. Medical and pharmaceutical applications: Titration is commonly used in medical and pharmaceutical labs to determine the concentration of drugs and compounds in solutions.
4. Water quality testing: Titration can be used to determine the pH of water, which is important in monitoring water quality for drinking and environmental purposes.

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