Question

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The OH-ion concentration in a certain ammonia solution is 7.2 x 10-M. What is the pOH and pH? Ans: 3.14 and 10.86 What is the H30* ion concentration in a solution with a pOH of 3.9? Ans: 8 x 10-11M The pH of many cola-type soft drinks is about 3.0. a) Calculate the [H3O+] in soft drinks. Ans: 1 x 10-3M b) How many times greater is the H30concentration in these drinks than in neutral water with pH 7.00? Ans: 10,000 times greater The pH of a certain solution is 3.0. How many moles of H3O+ (aq) ions are there in 0.10 L of this solution? Ans: 1 x 10-4 mol H30

Answer 1

given

[OH-]= 7.2 x10^-2 M
pOH - -log[OH-] =-log[7.2 x10^-2 M]
= 3.14
***********

pH +POH = 14
so pH = 14- 3.14
= 10.86
**************
2)

given
pOH = 3.9
pH = 14-3.9 = 10.1
[H3O+] = 10^-pH = 10^-10.1
= 8 x10^-11 M
*******************
3)
a)
given
pH = 3

[H3O+] = 10^-pH = 10^-3

= 1x10^-3 M
******************
b)
pH of water = 7

so [H3O+] = 10^-7 M

ratio of [H3O+]cola : [H3O=]water = 10^-3/10^-7 = 10^4

Thus [H3O+]cola is 10000 times greater
****************************************

4)
given
pH = 3
[H3O+] = 10^-3 mols/L

so moles of H3O+ in 0.1 L = 10^-3 * 10^-1 = 10^-4

thus answer is
1 x10^-4 mols
*****************