Multiple Choice
In the titration of a 35.0 mL sample of 0.175 M HBr with 0.210 M KOH, what is the pH after adding 5.0 mL of base beyond the equivalence point?
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18. Aqueous Equilibrium
Titrations: Strong Acid-Strong Base
Multiple Choice
Two 20.0-mL samples, one 0.200 M KOH and the other 0.200 M unknown base, are titrated with 0.100 M HI. What is the volume of added acid at the equivalence point for each titration?
A
40.0 mL for both KOH and the unknown base
B
40.0 mL for KOH and 20.0 mL for the unknown base
C
20.0 mL for KOH and 40.0 mL for the unknown base
D
20.0 mL for both KOH and the unknown base
Verified step by step guidance1
Identify the reaction involved in the titration. For KOH and HI, the reaction is: \( \text{KOH} + \text{HI} \rightarrow \text{KI} + \text{H}_2\text{O} \). This is a neutralization reaction where one mole of KOH reacts with one mole of HI.
Calculate the moles of KOH present in the 20.0 mL sample. Use the formula: \( \text{moles} = \text{concentration} \times \text{volume} \). Here, \( \text{concentration} = 0.200 \text{ M} \) and \( \text{volume} = 20.0 \text{ mL} = 0.0200 \text{ L} \).
Determine the volume of 0.100 M HI needed to reach the equivalence point for KOH. Since the reaction is 1:1, the moles of HI required will be equal to the moles of KOH. Use the formula: \( \text{volume of HI} = \frac{\text{moles of KOH}}{\text{concentration of HI}} \).
Repeat the calculation for the unknown base, assuming it also reacts in a 1:1 ratio with HI. Calculate the moles of the unknown base using its concentration and volume, then determine the volume of HI needed using the same method as for KOH.
Compare the calculated volumes of HI needed for both KOH and the unknown base to the given answer choices to determine the correct answer.
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