Q1: You have 21.7 mL of a 0.9 M solution of A. How many moles of A do you have?

Question

Q1:  You have 21.7 mL of a 0.9 M solution of A. How many moles of A do you have?

Q2: In a titration experiment, 9.3 mL of an aqueous HCl solution was titrated with 0.4 M NaOH solution. The equivalence point in the titration was reached when 9.5 mL of the NaOH solution was added. What is the molarity of the HCl solution?

Q3: In the titration of HCl with NaOH, the equivalence point is determined
a. from the point where the pink phenolphthalein turns colorless and then remains colorless on swirling.
b. from the point where the phenolphthalein turns pink and then remains pink on swirling.
c. from the point where the pink phenolphthalein first turns colorless and then the pink reappears on swirling.
d. from the point where the colorless phenolphthalein first turns pink and then disappears on swirling

Explanation / Answer

Q1. Moles =Molartiy ( moles/L) * Volume of the solution in lters (L) = 0.9*21.7/100=0.01953 moles

Q2. The reaction is HCl+ NaOH----> NaCl+ H2O

both HCl and NaOH are strong acid and base respectivley and NaCl is a salt which is neutral , i.e pH=7

At the equivalence point the moles of HCl and the moles of NaOH are equal.

The molar ratio od HCl : NaOH= 1:1

q3. At the equivalence point , pink phenolphtalein turns colorless and remains color less on swirling

(A is the correct answer)

Hence

9.3Molarity of HCl =molesof Hcl =0.4* 9.5.1000 moles of NaOH

Molarity of HCl =9.5*4/9.3 =0.4086M

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