Hi! Thank you for your help...
A 25.0 mL sample of 0.723 M HClO4 is titrated with a 0.273 M KOH solution. The H3O+ concentration after the addition of 66.2 mL of KOH is ______M. (The answer is supposed to be 1.00X10^-7)
How do I set this problem up? I realize that it is a strong acid-strong base titration, but I don't know what to do..
thanks!!
mole of the first one is M x L = 0.018075 which rounds to 0.0181 to three s.f.
mole of the second one is 0.0180726 which rounds to 0.0181 to three s.f.
So you are at the equivalence point of a strong acid/strong base so you have the salt (which is KClO4) and water. Therefore, the H^+ is determined by the ionization of water. The H^+ is 1 x 10^-7 M. The OH^- is 1 x 10^-7 M.
To solve this problem, you need to use the principles of stoichiometry and the concept of balanced chemical equations. Here's how you can set up and solve the problem:
1. Write the balanced chemical equation for the reaction between HClO4 and KOH. In this case, it is a neutralization reaction, so it can be written as follows:
HClO4 + KOH -> KClO4 + H2O
2. Determine the stoichiometry of the reaction. From the balanced equation, you can see that one mole of HClO4 reacts with one mole of KOH, forming one mole of KClO4 and one mole of water.
3. Calculate the number of moles of KOH added to the reaction using its concentration and volume. Given that the volume of KOH solution added is 66.2 mL and its concentration is 0.273 M, you can calculate the number of moles of KOH as follows:
moles of KOH = (0.273 M) * (66.2 mL / 1000 mL/L)
4. Since the stoichiometry of the reaction is 1:1, the number of moles of HClO4 reacted is equal to the number of moles of KOH added.
5. Calculate the volume of HClO4 using its concentration and the number of moles of HClO4 reacted. Given that the concentration of HClO4 is 0.723 M and the volume is 25.0 mL, you can calculate the number of moles of HClO4 using the equation:
moles of HClO4 = (0.723 M) * (25.0 mL / 1000 mL/L)
6. Calculate the concentration of H3O+ ions by dividing the number of moles of HClO4 by the total volume of the solution (initial volume + volume of KOH added). The total volume of the solution is:
Total volume = volume of HClO4 + volume of KOH added
7. Finally, calculate the H3O+ concentration:
H3O+ concentration = (moles of HClO4) / (Total volume)
Remember to convert the volume from mL to L before performing calculations.
By following these steps, you should be able to calculate the H3O+ concentration after the addition of 66.2 mL of KOH and find the answer to be 1.00x10^-7 M, as given.
To find the H3O+ concentration after the addition of the KOH solution, we can use the stoichiometry of the acid-base reaction and the concept of molar equivalence.
First, let's write the balanced chemical equation for the reaction between HClO4 and KOH:
HClO4 + KOH -> KClO4 + H2O
From the balanced equation, we can see that for every 1 mole of HClO4, 1 mole of H3O+ is produced. Therefore, the moles of HClO4 neutralized by the KOH can be calculated from the given volumes and concentrations.
Step 1: Calculate the moles of HClO4 initially present:
moles of HClO4 = volume (in L) x concentration
= 0.025 L x 0.723 mol/L
Step 2: Calculate the moles of KOH used in the titration:
moles of KOH = volume (in L) x concentration
= 0.0662 L x 0.273 mol/L
Step 3: Determine the moles of HClO4 neutralized by KOH:
Since the balanced equation shows a 1:1 stoichiometric ratio, the moles of HClO4 neutralized is equal to the moles of KOH used.
moles of HClO4 neutralized = moles of KOH
= 0.0662 L x 0.273 mol/L
Step 4: Calculate the moles of HClO4 remaining:
moles of HClO4 remaining = moles of HClO4 initially present - moles of HClO4 neutralized
Step 5: Calculate the volume of water formed:
Since the reaction produces water, the volume of water formed can be calculated using the ideal gas law. Assuming that the reaction proceeds completely and the water formed is in the gas state:
volume of water = moles of HClO4 neutralized x 22.4 L/mol
Step 6: Calculate the final volume of the solution:
final volume = initial volume + volume of water formed + volume of KOH added
Step 7: Calculate the final concentration of HClO4:
final concentration = moles of HClO4 remaining / final volume
Step 8: Calculate the final H3O+ concentration:
The H3O+ concentration is equal to the final concentration of HClO4.
H3O+ concentration = final concentration of HClO4
Substitute the calculated values into the equation to find the H3O+ concentration after the addition of the KOH solution, which should give 1.00 x 10^-7 M, as stated in the answer.