What is the concentration of an HCl solution if 23.1 mL of HCl are needed to neutralize completely 35.0 mL of 0.101 M Ba(OH)2
I cannot get the right answer
(Macic)(23.1mL)=(0.101M)(35.0mL)
Macid = .153
The problem is that the simplified formula you are using works ONLY for acids and bases that react 1:1. For example, in the titration of HCl and NaOH you have HCl + NaOH ==> NaCl + H2O and the formula you have shown works very well. In the case of HCl and Ba(OH)2; however, the reaction is
2HCl + Ba(OH)2 ==> BaCl2 + 2H2O
The best way to work these is to calulate moles of the base you have. That is M x L = 0.101 x 0.035 = 0.003535. Then using the coefficients to convert from moles Ba(OH)2 to moles HCl. It takes 2HCl to equal 1 Ba(OH)2 so moles HCl must be 2*0.0335 = 0.00707. Then M HCl = moles HCl/L HCl = 0.00707/0.0231 = ?
Many students don't like to use so many zeros (when using volumes in L --and I don't either) so I use millimoles.
millimoles = mL x M = ?
Then convert mmoles Ba(OH)2 to mmoles HCl. Finally M HC = mmoles/mL.
(Remember M = moles/L but if we multiply top and bottom by 1000, we get mmoles on top and mL on bottom)
To find the concentration of the HCl solution, you can use the principle of stoichiometry. Stoichiometry allows you to relate the amounts of reactants and products in a chemical equation. In this case, the reaction between HCl and Ba(OH)2 is as follows:
2HCl + Ba(OH)2 → BaCl2 + 2H2O
Based on the balanced equation, you can see that 2 moles of HCl react with 1 mole of Ba(OH)2. This means the molar ratio between HCl and Ba(OH)2 is 2:1.
Now, let's work through the problem step-by-step:
1. Determine the number of moles of Ba(OH)2:
Using the given concentration and volume, you can calculate the amount of Ba(OH)2 in moles.
moles of Ba(OH)2 = concentration × volume = 0.101 M × 35.0 mL = 0.101 × 0.0350 mol
2. Using stoichiometry, find the number of moles of HCl:
Since the ratio of moles between HCl and Ba(OH)2 is 2:1, we can conclude that the moles of HCl are also 0.101 × 0.0350 mol.
3. Finally, calculate the concentration of HCl:
Concentration of HCl = moles/volume = (0.101 × 0.0350 mol)/(23.1 mL).
Now, plug in the values and calculate:
Concentration of HCl = (0.101 × 0.0350 mol)/(23.1 mL) = 0.153 mol/L
Therefore, the concentration of the HCl solution is 0.153 M.
If you were not obtaining the correct answer, make sure you have used the appropriate units and followed the steps properly.