Question

Suppose that 0.10 liter of 0.50 molar hydrochloric acid is added to 0.040 liter of the buffer
prepared in (b). Compute the hydrogen ion concentration of the resulting solution.

Answer 1

First, let's find the moles of HCl added:

moles HCl = volume (in liters) x molarity
moles HCl = 0.10 L x 0.50 mol/L
moles HCl = 0.05 mol

Next, let's find the moles of the buffer components in 0.040 L:

moles of HA = volume (in liters) x molarity
moles of HA = 0.040 L x 0.50 mol/L
moles of HA = 0.020 mol

moles of A- = volume (in liters) x molarity
moles of A- = 0.040 L x 0.50 mol/L x 0.10
moles of A- = 0.002 mol

To calculate the hydrogen ion concentration of the resulting solution, we need to find the total moles of H+ and the total volume of the solution. The HCl will completely dissociate in water, so all of its moles will contribute to the hydrogen ion concentration:

total moles of H+ = 0.05 mol (from HCl) + 0.002 mol (from A-)
total volume = 0.10 L + 0.040 L = 0.14 L

Now we can calculate the hydrogen ion concentration:

[H+] = moles of H+ / volume of solution
[H+] = (0.05 mol + 0.002 mol) / 0.14 L
[H+] = 0.37 M

Therefore, the hydrogen ion concentration of the resulting solution is 0.37 M.