Why the graduated cylinder used to collect the glass should be moved so that the
ID: 921689 • Letter: W
Question
Why the graduated cylinder used to collect the glass should be moved so that the water level within it is at the same level of the water in the bath it is placed before reading the volume what are the units used for molar gas volume Know how to prepare a solution of KHP (KHC_8H_4O_2) and how to use it to "standardize a NaOH solution as in experiment 9. In addition know: Why the volume of the KHP solution does not affect the results when titrated with NaOH(aq). How to calculate the concentration of an unknown monoprotic acid from a titration with a standardized NaOH solution given all experimental data. Why it is important to stop adding NaOH when the first persistent color from the phenolphthalein appears. Why it is important to boil the water used to prepare the NaOH solution. Why it is important to use an acid sueh as KHP that can easily be made anhydrous by heating without decomposition and docs not absorb water rapidly. Know how to calculate the molar mass of volatile liquid as was done in experiment 9. For example: A 137 mL flask contains 0.481 g of a gas at 767 torr and 22degreeC. a) What is the molar mass of the gas? What is the density of the gas at STP?Explanation / Answer
Answer 15
a. Because we know the KHP grams and thus the moles of acid, which should equal the moles of NaOH to the equivalence point.
b. We use:
moles acid= moles base
Molarity acid*Vacid= Molarity base* Vbase
Molarity acid=Molarity base* Vbase/ Vacid
c. To avoid going over the endpoint and errors in quantifying the concentration of the acid.
d. To release the CO2 in the water. The CO2 dissolved in water lowers the pH and causes errors in the quantification of the concentration of acid.
e.Because to know exactly the composition of the KHP and ensure it does not spoil the light, does not absorb water, NaOH concentarción wll be determined more accurately.
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