Question

How many times more acidic is HI (hydroiodic acid) compared with HCl (hydrochloric acid).

Enter a whole number with no decimals. For example, if I wanted to say that HI was 5,000 times more acidic than HCl, I would enter only the number 5000 (without commas or decimals) as my answer.

TIP: use the pKa chart

Answer 1

First, get pKa vlaues, which are the measure of acidity

as Ka increases, this implies more H+ present in slution

pKa = -log(Ka) , therefre, the lower value of pKa the more acidic

Most common values:

HCl = -7 HBr = -9 HI = -10

Then

compare pK vlaues

ratio = Ka - HI / Ka - HCl

ratio = 10^-pKa -HI / 10^-pKa - HCl

ratio = 10^-(-10) / 10^-(-7)

ratio = 10^3 or 1000

i.e. the HI acid is 1000 stronger than HCl approx... depend on data given; just substitute your values with pKa values