7-9b 7. In the peocedure, a 4.00 g mass of NaOH is dissolved in 5.00 mL. of HiO

Question

7-9b

7. In the peocedure, a 4.00 g mass of NaOH is dissolved in 5.00 mL. of HiO What is the approximate molar concentration of the Na041? b. In the procedure, a 4.00 mL aliquot of this solution is diluned to 5.00 X10'ml- Wha is the approximate molar concentration of NaOH in the diluted solution? Record answer here as well as in lab assignment Calculate the mass of KHP (molar mass 204.44 g/mol) that reacts with 15 ml of the NaOH solution in the procedure. . Express mass of KHP with the correct number of significant figures. Record answer in lab assignmem. 8. A 0.41 1 g sample af KHP is dissolved with 50.00 mL of deionized iLO in a 125-mL Erlenmeyer ask. The sample is titrated to the endpoint with 15.17 mL of a NaOH solution. What is the molar concentration of the NaOH solution? Give answer to the correct number of significant figures. a. b. A 25.00 m aliquos of nitric acid (HNO,) of unknown concentration is pipetted into a 125- mL. Erlenmeyer flask and 2 drops of phenolplshalein are added. The above NaOH (itrant) solution is used to titrate the HNO, (analyte). If 16.77 ml. of titrant is used to reach the endpoimt, what is the molar concentration of the nitric acid? Give answer to the correct number of significant figures Prelaboratory Assignments

Explanation / Answer

Ans 7 :

Number oh moles of NaOH = 4 / 40 = 0.1 moles

a) Molarity = no. of moles / volume of solution in L

M = 0.1 / 0.005

M = 20 M

b) The number of moles of NaOH in 4.00 mL of aliquot will be :

n = Molarity x volume

n = 20 x 0.004

n = 0.08 moles

Molar concentration of dilute solution :

M = 0.08 / 0.5

M = 0.16 M

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