Question

Complete the following table for a selection of foods:

Food	[H3O+]	[OH−]	pH	Acidic,basic, orneutral?
Apple juice			3.80
Soy milk				neutral
Tuna (canned)	6.3×10−7M

Part A

Calculate the [H3O+] of apple juice with pH=3.80 .

Express the molarity to two significant figures.

Part B

Calculate the [OH−] of apple juice with pH=3.80 .

Express the molarity to two significant figures.

Answer 1

PH = 3.8

POH = 14-PH

         = 14-3.8 = 10.2

POH = 10.2

-log[OH-] = 10.2

     [OH-] = 10^-10.2   = 6.3*10^-11 M

   [H+]   = Kw/[OH-]

               = 1*10^-14/6.3*10^-11   = 1.58*10^-4 M

[H+] = 6.3*10^-7 M

PH = -log6.3*10^-7

        = 6.2

[OH-] = Kw/[H+]

          = 1*10^-14/6.3*10^-7    = 1.58*10^-8 M

Food	[H3O+]	[OH−]	pH	Acidic,basic, orneutral?
Apple juice	1.58*10-4 M	6.3*10-11 M	3.80	Acidic
Soy milk	10^-7	10^-7	7	neutral
Tuna (canned)	6.3×10−7M	1.58*10^-8	6.2	acidic