Question

1. Suppose 1.00 g of NaOH is used to prepare 250 mL of an NaOH solution. Compare the expected molarity of this solution to the actual average molarity you measured in the standardization. What do you notice?
2. Do you think the results would have been more accurate if a different type of acid or base were used in the standardization? Why, or why not?
3. There are many different primary standards that could be used in a standardization titration. What are the criteria for a primary standard?

PRE-LAB QUESTIONS
1.   What is the molar ratio of citric acid to sodium hydroxide (refer to the reaction equation)?
3:1 ratio
2.   Calculate the mass of sodium hydroxide needed to prepare 100 mL of a 0.100 M solution.
.400 g
3.   Calculate the mass of citric acid needed to react completely with 20 mL of a 0.100 M NaOH solution.
.129g
4.   Why is it important that the primary standard chemical be non-hygroscopic and pure? Why is it important to dry the primary standard to a constant weight?
It is important that the primary standard chemical be non-hygroscopic, pure and also have a constant weight so that the end point during the titration does not get affected. An error in the end point would result in errors in the subsequent calculations of concentration/mass.
5.   Use Figure 5 to determine which combination of acids and bases provides the most distinguishable equivalence point? Which combination is the most difficult to determine an equivalence point?
Combination of strong acid and strong base provides the most distinguishable equivalence point as in case of strong acid and bases they dissociate completely into H+ and OH- in the solution, which results in sharper titration curve and thus it becomes easy to locate the equivalence point.
Where as in case of weak acid and weak base it is completely reverse if the above. Weak acid and weak base do not dissociate completely in the solution so it not possible to predict the concentration of the dissociated and undissociated species and change in pH is not accounted accurately so it becomes very difficult to determine the equivalence point for this combination.

6.   Potassium hydrogen phthalate (KHP, KHC8H4O4) is also a good primary standard. 20 mL of NaOH was titrated with 0.600 M KHC8H4O4 solution. The data was graphed and the equivalence point was found when 15.5 mL of the standard 0.600 M KHP solution was added. The reaction equation is:

a.   What is the molar ratio of NaOH:KHC8H4O4?
Molar ratio is 1:1
b.   What is the molarity of the NaOH solution?
X = .467 moles/L NaOH
7.   Calculate the amount of sodium hydroxide you will need to make 250 mL of a 0.1 M solution of sodium hydroxide.
1 g of NaOH is needed.
 
EXPERIMENT 1: DETERMINING MOLARITY OF NaOH
Calculations
1.   Observe the graphs you plotted for each trial to determine the equivalence point in each trial. Refer to Figure 4 for reference.
a.   Trial 1 Equivalence Point: 1.5
b.   Trial 2 Equivalence Point: 1.5
2.   Determine the molarity of the NaOH solution in each trial.
a.   Trial 1 Molarity: 1.02m
b.   Trial 2 Molarity: 1.02 m
3.   Calculate the average molarity of the NaOH solution.
Average molarity is 1.02 M.

4.   Label the volumetric flask containing the NaOH solution with the average molarity.
X1                   y1
.5                   0
1   0
1.5   5.5
2   .7
2.5   .4
3   .5
3.5   .6

Data Sheet
Table 1: Part 1 Data
Mass of Beaker (Step 3; g)   Mass of Beaker + Citric Acid (Step 5; g)   Mass of Citric Acid (Step 4; g)   Mass of Beaker + Citric Acid After Cooling (Step 16; g)   Molarity of Citric Acid Solution (M)
96.3   98.3   2.0   98.3   6.8

Table 2: Trial 1 Data
Syringe reading (mL)   Citric Acid Added (mL)   pH
30   0.0   _13___ initial pH
29.5   .5   12.9
29   1   11.1
28.5   1.5   7.4
28   2   6.8
27.5   2.5   6.4
27   3   5.9
26.5   3.5   5.3
26   4   5.1
25.5   4.5   4.9
25   5   4.4
24.5   5.5   4.3
24   6   4.2
23   7   4.0

Table 3: Trial 2 Data
Syringe reading (mL)   Citric Acid Added (mL)   pH
30   0.0   _13___ initial pH
29.5   .5   13
29   1   13
28.5   1.5   7.5
28   2   6.8
27.5   2.5   6.4
27   3   5.9
26.5   3.5   5.3
26   4   5.0
25.5   4.5   4.9
25   5   4.6
24.5   5.5   4.3
24   6   4.2
23.5   6.5   4.1

Post-Lab Questions
1.   Suppose 1.00 g of NaOH is used to prepare 250 mL of an NaOH solution. Compare the expected molarity of this solution to the actual average molarity you measured in the standardization. What do you notice?
2.   Do you think the results would have been more accurate if a different type of acid or base were used in the standardization? Why, or why not?
3.   There are many different primary standards that could be used in a standardization titration. What are the criteria for a primary standard?

Answer 1

The post lab questions or the questions given at the start without numbers are experiment based, therefore, can not be answered. You need to provide your experiment details for the solutions.

Therfore, I have solved first question of the pre lab questions, that is, according to HomeworkLib policy, first doable question must be answered.