question 1.Your TA assigns you two monoprotic( one proton per molecule) acids HA

Question

question 1.Your TA assigns you two monoprotic( one proton per molecule) acids HA and HB. You are given 43.5 mL of HA solution in the first flask. A second flask contains 37.2 mL of HA and enough HB solution is added to reach a final volume of 50.0mL. You titrate the HA solution, in the first flask, with 87.3mL of 0.0906 M NaOH. What is the molarity of the acid HA? ( Write answer to two decimal places, ex. 1.25 )

question 2.Your TA assigns you two monoprotic( one proton per molecule) acids HA and HB. You are given 43.5 mL of HA solution in the first flask. A second flask contains 37.2 mL of HA and enough HB solution is added to reach a final volume of 50.0mL. You titrate the second flask, containing HA and HB with 96.4mL of 0.0906 M NaOH. What is the molarity of the acid HB?  ( Write answer to two decimal places, ex. 1.25 )

( Hint: You will need to use the answer from the previous question)

Explanation / Answer

Given : Two monoprotic acids :

Volume in first flask : HA = 43.5 mL = 0.0435 L

Volume in second flask : HA : 0.0372 L + x mL HB = 50.0 mL

Volume of NaOH = 0.0906 M volume of NaOH = 87.3 mL = 0.0873 L

Molarity of acid A

Lets write the reaction between HA and NaOH

NaOH (aq) + HA (aq) --- > NaA (aq) + H2O (l)

Molarity of acid HA = Number of moles HA / volume in L

Number of moles of NaOH = Molarity x volume in L

= 0.0906 M x 0.0873 L = 0.007909 mol

Moles of acid = 0.007909 mol NaOH x 1 mol HA / 1 mol NaOH

= 0.007909 mol HA

[HA]= 0.007909 mol / 0.0435 L = 0.182M

Q. 2 :
50.0 mL = 43.5 mL HA + x mL HB

Volume of NaOH needed for the titration of second flask = 96.4 mL

Molarity of NaOH = 0.0906 M

Moles of NaOH = 0.0906 M x 0.0964

= 0.0087 mol NaOH

Lets calculate moles of acid from flask two

Moles of acid = moles of NaOH x 1 mol acid (HA + HB)/ 1 mol NaOH

= 0.0087 mol (HA+ HB)

Number of moles of (HA+ HB) = 0.0087

Lets calculate moles of HA

Moles of HA = molarity x volume in L = 0.182 M x 0.037 L = 0.006734 mol

Moles of HB = 0.0087 – 0.006734 = 0.002 mol

[HB]= 0.002 mol / (0.050-0.0370) = 0.154 M

Related Questions

Navigate

• Browse (All)
• Browse Q
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.