For number 4, a-e. I need help setting up my calculations. What numbers do I nee
ID: 698832 • Letter: F
Question
For number 4, a-e. I need help setting up my calculations. What numbers do I need to calculate these pH? This is for an acid base titration lab in which we had a ph meter in the solution. But it looks like it also wants us to calculate the pH which I’m having trouble with. Thank you !!ata Show all calculations in an organized and clear fashion. You should prepare a plot of each titration by plotting pH (y-axis) vs volume (x-axis) of base using Excel or other spreadsheet in which you can graph your data. Graphs should be one full page and the axes should be labeled with names and units. Instructions for using Microsoft Excel are given at the end of this experiment. The equivalence point of reaction is the point at which a stoichiometric equivalent number of moles of the reactants have been added. It can be located by conducting a visual inspection of the titration curve and locating the inflection point. What is the volume of the equivalence point of your titration? This answer must be based on data from your graph and not a volume calculation. 1· The equivalence point can also be located on a pH vs. volume graph using a first derivative plot. The equivalence point will appear as the highest point on the first derivative curve. Make a first derivative plot of your pH vs Volume graph. What is the volume of the equivalence point of your titration? 2. To be a good indicator, the visual change must occur on the steep portion of the graph. Decide if the indicator that you used was a good choice for this experiment. If an indicator changes too soon, it is called an early indicator and of course, one that changes afterwards is called a late indicator. Which class does your indicator fall into? 3. Calculate the pH of your sample at several points during the titration. In each case, record your calculated pH and your experimentally observed pH 4. Calculate the initial pH of your sample before any titrant was added. (Do not forget that you added some DI water to your sample before you began titrating.) Record your calculated pH value below and the experimentally observed value from your graph. a. Calculated: b. Record your calculated pH Calculate the pH after 7.00 mL of NaOH was added. value below and the experimentally observed value from your graph. Observed: Calculate the pH at 1.00 mL of NaOH added prior to the equivalence point. Record your calculated pH value below and the experimentally observed value from your graph. Calculated c. Calculated d. Calculate the predicted pH at the measured Veq. Record your calculated pH value below and the experimentally observed value from your graph. Calculated Calculate the pH at 7.00 mL of NaOH added after the Veq. calculated pH value below and the experimentally observed value from your graph. Observed: e. Record your Calculated: 128
Explanation / Answer
For these calculations, you need to know the concentration and volume of the acid you are using and the concentration of base.
To calculate the pH intially: If it is a strong acid, then use the formula, pH = -log[H+], where [H+] is the concentration of the acid you are using. And if the acid is weak, then you also need to know the Ka (acid dissociation constant) for that particular acid and you will be drawing the ICE table to calculate pH.
To calculate pH of the solution after addition of some volume, you need to calculate first the moles of base and acid each. And then you have to see that how many moles of base is left to calculate the pH of the solution.
After equivalence point, whole of acid has been neutralised, so pH will be only due to base. So, you can do this directly from the moles of NaOH.
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