mols of HCl= 0.1N X 0.5L=0.05 mols of HCl
Therefore, number of mols of 2N NaOH needed to obtain pH 6.8:
0.05 mols HCL/2 = 25 mL
Is this right?
answered below.
To determine the number of moles of HCl, you used the formula:
moles of HCl = (normality of HCl) x (volume of HCl)
Given that the normality of HCl is 0.1N and the volume of HCl is 0.5L, you calculated:
moles of HCl = 0.1N x 0.5L = 0.05 moles of HCl
Your calculation for the moles of HCl is correct.
To find the number of moles of 2N NaOH required to obtain pH 6.8, you divided the number of moles of HCl by 2. This step is not clear from your explanation, but assuming the basis of this calculation is that the reaction between HCl and NaOH is 1:1, let's analyze it.
If the reaction between HCl and NaOH is 1:1, then the 0.05 moles of HCl will require an equal number of moles of NaOH to react completely. Therefore, the moles of 2N NaOH required would also be 0.05 moles.
However, in your explanation, you mention that the 0.05 moles of HCl corresponds to 25 mL of 2N NaOH. This calculation seems to imply a different molar ratio between HCl and NaOH.
Therefore, your calculation of 0.05 moles of 2N NaOH corresponding to 25 mL is not accurate. To determine the volume of 2N NaOH required, you would need to know its concentration in moles per liter (mol/L) and then use the equation:
moles of NaOH = (moles of HCl) x (volume of HCl) / (concentration of NaOH)
Without the concentration of NaOH in mol/L, we cannot accurately calculate the volume of 2N NaOH needed to obtain a pH of 6.8.