Note : some questions will display a variable like "nCount" or "SyInput" instead of an actual number in the data summary. Q# Question Text

5) Data Entry - No Scoring

Enter the precise mass in GRAMS of the potassium iodate used to prepare your primary standard solution. Your mass precision should be reported to a thousandth of a gram, i.e. 0.302. (Use 3 significant figures.) Your Answer: 0.536

No Points Possible

6)

Scoring Scheme: 3-3-2-1

If one had weighed out precisely 0.500 g of KIO3 for the primary standard solution and dissolved it in enough deionized water to make a 250 mL solution, the molarity of that solution would be 0.00935 M. Enter your calculated molarity of the primary standard KIO3 solution. Please use 3 significant figures. Your Answer: 0.01

You Scored 3 points out of 3 Possible

7)

Data Entry - No Scoring

Standardization of the sodium thiosulfate solution using the potassium iodate primary standard solution. We must examine each of the three acceptable trials.

First, let's consider the analyte volume. You were instructed to pipet two 10.00 mL aliquots of potassium iodate into an Erlenmeyer flask for each analyte sample to be titrated. Therefore, your analyte volumes of the potassium iodate should be 20.00 mL.

For each trial, enter the precise volume in mL of potassium iodate solution used in the standardization of sodium thiosulfate (e.g. 20.00 mL or 10.00 mL):

Your Answer: 20

No Points Possible

Your Answer: 20

No Points Possible

Your Answer: 20

No Points Possible

8)

Data Entry - No Scoring

Standardization of the sodium thiosulfate solution using the potassium iodate primary standard solution. Now we will examine the volumes of titrant, sodium thiosulfate, used in each trial. Your titration volumes of the sodium thiosulfate solution should be approximately 20 - 30 mL. For each trial, enter the precise volume in mL of sodium thiosulfate solution used in the titration of your potassium iodate solution (e.g. 20.34 mL):

Your Answer: 23.3

No Points Possible

Your Answer: 23.33

No Points Possible

Your Answer: 22.65

No Points Possible

9)

Scoring Scheme: 3-3-2-1

Using the volumes of sodium thiosulfate solution you just entered and the molarity of the potassium iodate primary standard solution, calculate the molarity of the sodium thiosulfate secondary standard solution for each trial.

Enter your calculated molarity of the sodium thiosulfate solution for each of the trials. Be sure to enter your calculated molarities in the corresponding order that you entered your sodium thiosulfate volumes previously. The sodium thiosulfate volume you entered for entry #1 above should correspond to the sodium thiosulfate molarity that you enter for entry #1 here.

Your Answer: 0.0515

Your Answer: 0.0514

Your Answer: 0.053

You Scored 3 points out of 3 Possible

No Points Possible

No Points Possible

10) Scoring Scheme: 3-3-2-1

The molarity of the sodium thiosulfate solution is taken as the average of the three trials. Please enter the average molarity.

Average =

Your Answer: 0.052

You Scored 3 points out of 3 Possible

11) Scoring Scheme: 3-3-2-1

Please enter the standard deviation of the sodium thiosulfate molarity. Standard Deviation =

Your Answer: 0.0009

You Scored 3 points out of 3 Possible

13) Scoring Scheme: 3-2-1-1

For the reaction of hypochlorite anion with iodide anion, the iodide anion acts as the reducing agent according to the oxidation half-reaction, 2I-(aq) -> I2(aq) + 2e-.

Which of the following reduction half-reactions is correct to give the overall reaction of hypochlorite anion with iodide anion?

You Scored 3 points out of 3 Possible

Your Answer: c. 2H+(aq) + ClO-(aq) + 2e - -> Cl-(aq) + H2 O(l) 14) Scoring Scheme: 3-2-1-1

For the reaction of thiosulfate anion with iodine, the thiosulfate anion acts as the reducing agent according to the oxidation half-reaction, 2S2O32-(aq) -> S4O62-(aq) + 2e-. Which of the following...

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