Post-Laboratory Questions alse the spaces provided for the answers and additiona
ID: 483819 • Letter: P
Question
Post-Laboratory Questions alse the spaces provided for the answers and additional paper if necessary) 1. Briefly comment on the effect, if any, the following procedural changes would have on the observations you made while doing this experiment. a) You poured too much o.1M NH,/Hzo solution into test tubes M1 and N2, leaving only 1 mL of the solution in test tube 3. You added phenolphthalein indicator solution as directed. You poured too much 0.1M NH,/Hzo solution into test tubes a1 and #2, so you added 2 mL Hzo to the solution in test tube #3 to bring the total solution volume to 3 mL You added phenolphthalein indicator solution as directed. (3) You added only 1 drop of phenolphthalein indicator solution to 3 mL of NH3/Hzosolution in test tube #3.
Explanation / Answer
Q1.
(1)
addition of excess of NH3 will increase the pH, phenolphtalein will have a pH change around 9, if excess base is added, the phenolphtalein will turn transparent again
(2)
Addition of H2O, won't fix the excess of NH3, since they are not additive. therefore the test tube #3 will be affected with a higher pH
(3)
No problem, 1 dorp is enough; therefore, expet no change