Open Question
A 25.0 ml sample of 0.125 moll−1 pyridine (kb=1.7×10−9) is titrated with 0.100 moll−1hcl.
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18. Aqueous Equilibrium
Titrations: Diprotic & Polyprotic Buffers
Multiple Choice
30.00 mL of a strong, diprotic acid are titrated with 0.1432 M NaOH. If it takes 24.15 mL to reach the endpoint of the titration, what is the concentration of the acid?
A
0.0716 M
B
0.0576 M
C
0.1144 M
D
0.0288 M
Verified step by step guidance1
Identify the type of acid involved in the titration. Since it is a diprotic acid, it can donate two protons (H⁺ ions) per molecule.
Write the balanced chemical equation for the reaction between the diprotic acid (H₂A) and NaOH. The equation is:
Calculate the moles of NaOH used in the titration. Use the formula: moles of NaOH = concentration of NaOH × volume of NaOH in liters. Convert 24.15 mL to liters by dividing by 1000.
Determine the moles of the diprotic acid (H₂A) that reacted. Since the stoichiometry of the reaction is 1:2 (1 mole of H₂A reacts with 2 moles of NaOH), divide the moles of NaOH by 2 to find the moles of H₂A.
Calculate the concentration of the diprotic acid. Use the formula: concentration of H₂A = moles of H₂A / volume of H₂A in liters. Convert 30.00 mL to liters by dividing by 1000.
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