5 Steps to a 5 AP Chemistry

322  STEP 5. Build Your Test-Taking Confidence

Question 5.

(a) *analytical balance *buret clamp

desiccator drying oven *Erlenmeyer flask

pH meter pipet support stand

wash bottle

You get 1 point if you have ALL the starred items. You get 1 point for the other items. There is a max-

imum of 2 points. If you have only some of the starred items, your maximum is 1 point.

(b)

You get 1 point for this graph. You get 1 point for noting that the equivalence point is greater than 7.

(c)

You get 1 point for this graph. You must show two regions.

(d) 1. Weigh a sample of HA.

2. Titrate HA versus standard NaOH to find the volume of NaOH solution required to neutralize the
   acid.


3. Multiply the concentration of the NaOH solution times the volume used to get the moles of
   NaOH.


4. The moles of HA is the same as the moles of NaOH.


5. Divide the mass of HA by the moles of HA.

You get 2 points if you list all five steps. If you miss one or more steps you get only 1 point. You get

0 points if you get none of the steps correct. There are no bonus points for more steps or more details.

(e) If the KHP contained an inert impurity, the concentration of the NaOH solution would be too low.

If the concentration of the NaOH solution were too low, then more solution would be needed for the

titration of HA. This would yield a lower number of moles of HA, giving a higher molar mass.

pH 7

pH > 1

Volume Added

Equivalence point at pH > 7