Final answer:
To determine the millimoles of HBr present, the equivalence point volume of NaOH was used to calculate the moles of NaOH, which is equal to the moles of HBr due to the 1:1 stoichiometry. The result is 1.93728 millimoles of HBr.
Step-by-step explanation:
The question asks how many millimoles (mmol) of HBr are present in a solution, given that it is titrated with a known concentration and volume of NaOH. This process is known as a titration and it involves neutralizing an acid with a base. To solve this, we will use the information that the equivalence point was reached when 15.62 ml of 0.124 M NaOH was added to the HBr solution.
First, calculate the moles of NaOH used at the equivalence point:
- Moles of NaOH = Volume (L) × Molarity (M)
- Moles of NaOH = 0.01562 L × 0.124 M
- Moles of NaOH = 0.00193728 mol
Since HBr is a strong acid and NaOH is a strong base, they react in a 1:1 molar ratio. Therefore, the moles of HBr initially present are equal to the moles of NaOH used to reach the equivalence point.
Millimoles of HBr = Moles of HBr × 1000
Millimoles of HBr = 1.93728 mmol
Therefore, there were 1.93728 millimoles of HBr in the original 10.0 ml solution.