Problem 15.83 with feedback Constants Periodic Table Part A Acid FormulaKa Formi
ID: 574317 • Letter: P
Question
Problem 15.83 with feedback Constants Periodic Table Part A Acid FormulaKa Formic HCO2H 1.8 x 10 Hydrocyanic HCN 4.9 x 10-10 Perchloric HCIO very large Hypobromous HOBr 2.0 x 10 9 Use the given values of Ka to arrange the following acids in order of decreasing acid strength Rank the acids from strongest to weakest. To rank items as equivalent, overlap thenm Reset Help You may want to reference (Pages 627- 628) Section 15.10 while completing this problem Hypobromous Perchloric HydrocyanicFormic Strongest acid Weakest acid SubmitExplanation / Answer
acid dissociation constant is an indication of strengh of an acid. Higher the dissociation constant, higher the acidty of the acid. Stronger acids will have larger dissociation constant.
hence HClO4> HCO2H>HOBr>HCN ( from acid strength point of view).
Higher the dissociation constant, more the percent dissociation.
hence HClO4>HCOOH>HOBr>HCN( from dissociation point of view)
for HClO4 at 1.9M,
hence [H3O+] = -log (1.9)= -0.28, strong acid with concentration >1M can have pH <0
if HA denoted the acid underconsideration
HA undergoes dissociation as HA+ H2O-------->H3O+ + A-
Ka= [H3O+] [A-]/[HA]
let x= concentration of A- at equilibrium, at equilibrium, [HA]= 1.9-x, [H3O+]= [A-]=x
hence Ka= x2/(1.9-x)
for HCOOH ,Ka= 1.8*10-4= x2/(1.9-x), when solved using excel, [H3O+]= 0.0184, pH= 1.73
for HOBr, Ka= 2*10-9= x2/(1.9-x), when solved using excel, [H3O+]= 6.17*10-5, pH= 4.21
for HCN, Ka= 4.9*10-10=x2/(1.9-x), when solved using excel, [H3O+]=30.5*10-6, pH= 4.52