0.682g of an unknown weak acid HA was dissolved in sufficient water to make 50mL off solution.the HA solution was titrated with 0.135M NaOH sol. after the additon og 10.6mL of base, aph of 5.65 was record. the equivalence point was reached after the addittion of 27.4mL of the 0.135M NaOH .(Ka for HA is 1.4x 10^-6)
a) what is the pH of solution when the original cid solution is half-neutralized?
b) calculate the pH of the solution at equivalent point

Question

0.682g of an unknown weak acid HA was dissolved in sufficient water to make 50mL off solution.the HA solution was titrated with 0.135M NaOH sol. after the additon og 10.6mL of base, aph of 5.65 was record. the equivalence point was reached after the addittion of 27.4mL of the 0.135M NaOH .(Ka for HA is 1.4x 10^-6) 
a) what is the pH of solution when the original cid solution is half-neutralized?
b) calculate the pH of the solution at  equivalent point

jfraser · Answer

since you know the volume and concentration of base used to reach the equivalence point, that will tell you the moles of base used.

since the acid is monoprotic, the moles of acid will be equal to the moles of base used to reach the equivalence point.

divide the mass by the moles and you'll get molar mass.

use the KA and the pH to find the concentration of H+ ions, then insert them into an ICE table to find the concentration of remaining acid