Question

calculate [H3O+], [OH-], for each of the following. Label the solution acidic, basic, or neutral

1. 0.01 M HCl

2. 0.033 M HNO3

3. 0.0045 M NaOH

4. 10 M HCl

5. 2.7 M NaOH

Answer 1

Irrrespective of molarity, a strong acid is strong and a strong base is strong.

1. pH=-log [H+]=-log [H3O+]

HCl is strong acid and ionizes completely.

[H3O+] =0.01

pH= -log(0.01)=2 pOH= 14-2= 12, -log[OH-] =12 , [OH-] =10^-12

2. HNO3 is also strong [H3O+]=0.033, pH= -log(0.033)=1.48 pOH= 14-1.48=12.52 [OH-]= 10^(-12.52) =3.019*10^-13

3. [OH-] =0.0045 for NaOH. a strong base. p[OH-]= -log(0.0045)=2.35

pH= 14-2.35=11.65

4. HCl is strong and [H+] =10 , pH=-log [10] =-1, pOH= 14-(-1)= 15

5. 2.7M NaOH , [OH-] =2.7, poH= -log (2.7)=-0.43 , pH= 14-POH= 14.43