Strong Acids and Bases. Note. It is important that you don't confuse the words strong and weak with the terms concentrated and dilute . As you will see, the strength of an acid is related to the proportion of it that has reacted with water to produce ions.
HA + H2O H3O+ + A-
HCl + H2O H3O+ +Cl-
There are four ways to describe a strong acid:
Calculate the pH of an aqueous solution containing 2.5x10-5M of HCl.
So first write the dissociation expression with HCl and water
HCl + H2O H3O+ + Cl-
Second, since we know that all the HCl will be converted to products, because HCl is a strong acid, we know that the concentrations of H3O+ and Cl- will be the same as the original acid.
All we need to do now is plug the value into the pH equation
Recall from yesterday pH=-log[H3O+]
Doing so we get
LiOH, NaOH,KOH, RbOH and CsOH(only NaOH and KOH are common because the others are expensive to work with)
Group IIA- Ca(OH)2, Ba(OH)2, Sr(OH)2
For these soultions 2 moles of hydroxide ion is produced for every 1 mole of metal hydroxide dissolved in aqueous solution.
Much the same as acids, there are
four ways to describe a strong base:
Calculate the pH of a 5.0x10-2M KOH
So first write the dissociation expression with KOH and water
KOH K+ + OH-
Second, since we know that all the KOH will be converted to products, because KOH is a strong base, we know that the concentrations of K+ and OH- will be the same as the original base
All we need to do now is find pOH and use the realtionship between pOH and pH
Recall from yesterday pOH=-log[OH-]
Doing so we get
Next subtract from 14 to get pH