Question 9 of 10 Sapling Learning Map A Strong base is dissolved in 7 Assume tha
ID: 501975 • Letter: Q
Question
Question 9 of 10 Sapling Learning Map A Strong base is dissolved in 7 Assume that the volume remains constant when the base is added. HA(aq)+ OH (aq Calculate the pKa value of the acid and determine the number of moles of acid initially present. Number Number pK, mol HA When the reaction x 10 what is the concentration ratio of conjugate base to acid? Number HA How many moles of strong base were initially added? Number mol OH A Previous 8 Give Up & view Solution Check Answer 0 Next a Exit Hint about us careers partners l privacy policy terms of use contact us helpExplanation / Answer
Pka value of acid:
Pka = -log[Ka]
Pka = -log(3.21*10-5)
Pka = 4.49
The number of mole of acid initially present = concentration * volume (in L)
= 0.2 M * 0.765 L
= 0.153 mol
The concentration ratio of conjugate base to acid when the reation is complete:
pH =Pka + log [A-]/[HA]
4.08 =4.49 + log [A-]/[HA]
[A-]/[HA] = 0.389
Number of moles of base added initially
[HA] = 0.153 mol
[A-] / 0.153 = 0.389
[A-] = 0.153 * 0.389 = 0.0595 mol of OH-