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Multiple Choice
Consider the titration of a 23.0 mL sample of 0.120 M RbOH with 0.100 M HCl. Determine the pH after adding 4.3 mL of acid beyond the equivalence point.
A
1.98
B
7.00
C
2.50
D
12.02
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1
Calculate the initial moles of RbOH in the solution using the formula: \( \text{moles of RbOH} = \text{volume (L)} \times \text{molarity (M)} \). Convert 23.0 mL to liters by dividing by 1000.
Determine the moles of HCl added at the equivalence point using the formula: \( \text{moles of HCl} = \text{volume (L)} \times \text{molarity (M)} \). The volume at equivalence point is equal to the initial moles of RbOH divided by the molarity of HCl.
Calculate the total moles of HCl added beyond the equivalence point by adding the moles of HCl from the additional 4.3 mL to the moles at the equivalence point. Convert 4.3 mL to liters by dividing by 1000.
Determine the excess moles of HCl after the equivalence point by subtracting the initial moles of RbOH from the total moles of HCl added.
Calculate the pH of the solution using the formula: \( \text{pH} = -\log[\text{H}^+] \), where \([\text{H}^+]\) is the concentration of excess HCl in the total volume of the solution (initial volume of RbOH + total volume of HCl added).