# AP CHEMISTRY HELP

posted by Amber

a) A student fails to wash the weighing paper when transferring the KHP sample into the beaker. What effect does this error have on the calculated molarity of the NAOH solution? Mathematically justify your answer.

b) A student failed to notice an air bubble trapped in the tip of the buret during their experiment. What effect does this error have on the calculated molarity of the NaOH solution. Mathematically justify your answer.

1. DrBob222

I think the best way to answer this type question is to write the steps involved in the procedure. Here is the KHP/NaOH problem.
1. mols KHP = grams/molar mass
2. mols NaOH = mols KHP
3. M NaOH = mols NaOH/L NaOH

I presume not washing the paper on which the KHP was weighed means some of the KHP was not transferred to the titration flask. That means mass KHP is low. From step 1 that means mols KHP is low. Step 2 says mols NaOH is low. Step 3 says M is low.
(For what's it's worth, I NEVER used weighing paper; as a result I never had that problem.)

2. Amber

Thank you so much. Also, would this same procedure be used for when there's an air bubble in the titration?

3. DrBob222

Yes. Just go through and determine how each step is affected, take that answer and move to the next step, then continue until you end up with the last step.

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