In neutral water at #298*K#, the following equilibrium operates:
#2H_2O(l) rightleftharpoons H_3O^+ + HO^-#
Careful measurement has established that at #298*K#, the ion product, #[H_3O^+][""^(-)OH]=10^(-14)#.
If the solution is neutral then, #[H_3O^+]=[""^(-)OH]=10^(-7)mol*L^-1#.
If #[H_3O^+]<[""^(-)OH]#, then the solution is alkaline, and if #[H_3O^+]>[""^(-)OH]#, then the solution is acidic.
We can go a step farther than this, and define #pH# and #pOH#. If we take #-log_10# of both sides of the equation,#[H_3O^+][""^(-)OH]=10^(-14)#, we get #-log_10[H_3O^+]-log_10[""^(-)OH]=-14#.
If we define #pH=-log_10[H_3O^+]# and #pOH=-log_10[""^(-)OH]#, then,
#pH + pOH =14.#
From above, at neutrality, #pH = pOH =7#; i.e. #[H_3O^+]# and #[HO^-]# are EQUAL.
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Terms in this set (10)
Substances of acidic or alkaline nature dissolve in water and/or contain:
a) salt
b) water (correct)
c) carbon
d) hydrogen
A solution that has more positive hydrogen ions than negative hydroxide ions is:
a)
acidic (correct)
b) neutral
c) alkaline
d) slightly alkaline
When a solution has an equal number of hydrogen and hydroxide ions, the solution is considered:
a) acidic
b) neutral (correct)
c) positive
d) negative
Distilled water with a pH of 7 is considered:
a) a salt
b) neutral (correct)
c) an
acid
d) an alkali
On the pH scale, numbers less than 7 indicate a(n):
a) acidic solution (correct)
b) neutral solution
c) chemical solution
d) alkaline solution
On the pH scale, numbers greater than 7 indicate a(n):
a) acidic solution
b) neutral solution
c) chemical solution
d) alkaline solution
(correct)
A pH of 5 is how many more times acidic than a pH of 6?
a) 1.5
b) 10 (correct)
c) 100
d) 1000
The most accurate method of measuring pH is with:
a) a pH meter (correct)
b) pH paper
c) indicator paper
d) indicator liquid
What is the pH range of hair, skin and nails?
a) 4.5 to 5.5 (correct)
b) 6.5 to 7.0
c) 7.5 to 10.5
d) 11.5 to 12.0
pH balanced refers to a product that ranges from a pH of:
a) 4.5 to 5.5 (correct)
b) 6.5 to 7.0
c) 7.5 to 10.5
d) 11.5 to 12.0
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