15ml of 0.325M NaOH is delivered into 35ml HOBr solution of unknown concentration.The pH of the final solution is 7.48. Ka for HOBr is 2.0 x 10-9at 25C. Find the number of moles of OBr- and HOBr in the final solution.
I would use the Henderson-Hasselbalch equation to determine the ratio of base to acid. Assuming all of the NaOH is converted to base, then OBr^- will be moles NaOH and you can use the ratio from the HH equation to determine moles of the acid.
To find the number of moles of OBr- and HOBr in the final solution, we need to go through the following steps:
Step 1: Calculate the number of moles of NaOH used.
Given that the volume of NaOH solution is 15 ml and the concentration is 0.325 M, we can use the formula:
Moles of solute = Concentration × Volume
Moles of NaOH = (0.325 M) × (15 ml) / 1000 ml/L
Step 2: Determine the excess OH- after the reaction.
Since NaOH is a strong base and HOBr is a weak acid, we need to determine how much of the OH- reacts with HOBr. We can do this by writing a balanced chemical equation for the reaction between NaOH and HOBr:
NaOH + HOBr → NaOBr + H2O
The balanced equation shows that one mole of NaOH reacts with one mole of HOBr, producing one mole of NaOBr and one mole of water.
Step 3: Calculate the concentration of HOBr in the final solution.
To find the concentration of HOBr in the final solution, we need to know the initial concentration of HOBr and the moles of HOBr that react with NaOH. The moles of HOBr that react with NaOH can be determined by the stoichiometry of the balanced equation. We know that one mole of NaOH reacts with one mole of HOBr, so the moles of HOBr that react with NaOH is equal to the moles of NaOH used.
Since the final volume of the solution is the sum of the volumes of NaOH and HOBr, we can use the formula:
Concentration of HOBr = Moles of HOBr / Final volume
Step 4: Calculate the concentration of OBr- in the final solution.
Since one mole of HOBr reacts with one mole of NaOH to produce one mole of OBr-, the moles of OBr- present in the final solution will be equal to the moles of NaOH used. Hence, we can obtain the concentration of OBr- in the final solution using the formula:
Concentration of OBr- = Moles of OBr- / Final volume
Step 5: Convert the concentrations to moles.
To calculate the number of moles of HOBr and OBr-, we multiply their concentrations by the final volume of the solution.
Once we have the moles, we can convert them to grams or any other units if needed.
Remember to use the ideal gas law if the final volume of the solution is significantly different from 1 liter, as this law assumes that the volume is 1 liter.
Given all the necessary calculations, you can now apply these steps to find the number of moles of OBr- and HOBr in the final solution.