QUESTION 1 5 points Save Answer Calculate the molarity of 87.69 ml of diluted Na

Question

QUESTION 1 5 points Save Answer Calculate the molarity of 87.69 ml of diluted NaOH solution prepared from 20.39 ml of 6.86 M NaOH stock solution. QUESTION 2 s pointsSave Answer f 32.73 ml of 0.0834 M hydrochloric acid requires 19.74 ml of the NaOH solution to reach the endpoint, what is the molarity of the NaOH solution? QUESTION 3 1 points Save Answer Correct procedures for a titration include which of the following? I. Rinsing the buret before beginning your titration with the solution that you use to titrate the sample Il. Rinsing the buret with tap water before filling the buret with the solution you will be using for the titration III. Swirling (mixing) the solution in the Erlenmeyer flask frequently during the titration and ill only QUESTION 4 1 points Save Answer Which piece of laboratory equipment is used to add small, precisely measured volumes of liquid to a solutions? Oa volumetric pipet Ob disposable pipet Oe graduated cylinder Od buret QUESTION S 1 points Save Answe According to the Safety Data Sheet (SDS). 6M NaOH solution is: O an irritant O odorless Oe comosive ans may cause irritation and damage to your skin and eyes upon prolonged contact O* all of the above

Explanation / Answer

Ans. #1. Using           C1V1 (Stock solution) = C2V2 (dilute solution)

            Or, 6.86 M x 20.39 mL = C2 x 87.69 mL

            Or, C2 = (6.86 M x 20.39 mL) / 87.69 mL

            Or, C2 = 1.595 M

Hence, molarity of diluted solution = 1.60 M

#2. Balanced reaction:         HCl(aq) + NaOH(aq) -------> Na+(aq) + Cl-(aq) + H2O(l)

Stoichiometry: 1 mol HCl is neutralized by 1 mol NaOH.

So, at equivalence of point-

            Moles of HCl = Moles of NaOH

            Or, (Molarity x Volume in liters) of HCl = (Molarity x Volume in liters) of NaOH

            Or, 0.0834 M x 0.03273 L = C2 x 0.01974 L

            Or, C2 = (0.0834 M x 0.03273 L) / 0.01974 L

            Hence, C2 = 0.138 M

Therefore, molarity of NaOH solution = 0.138 M          

#3. Correct option. b. I, II and III

The burette must be first rinsed with distilled water to remove any contaminant present in it.

Second, the burette shall be rinsed with the same solution to be used to titrate the sample. This rinsing removes the traces of water present in burette in first step. Thus, this step is crucial to eliminate the contamination of solution (used for titrating the sample with water and subsequent lowering of its concertation.

Frequent swirling of the Erlenmeyer flask mixes the sample and titrant solution and is crucial for getting precise end points.

#4. Correct option. a. Volumetric pipettes.

Volumetric pipettes are class A pipettes which can deliver a solution with accuracy of four significant figures.

#5. Correct option. D. all of the above.

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