General Chemistry Principles, Patterns, and Applications, 2011

a. Sodium hydroxide is an ionic compound that is a strong electrolyte (and a strong base)
in aqueous solution:
NaOH(s) → H 2 O(l) Na + (aq) + OH – (aq)
B Because each formula unit of NaOH produces one Na + ion and one OH − ion, the concentration of
each ion is the same as the concentration of NaOH: [Na + ] = 0.21 M and [OH − ] = 0.21 M.
b. A The formula (CH 3) 2CHOH represents 2-propanol (isopropyl alcohol) and contains the –
OH group, so it is an alcohol. Recall from Section 4.1 "Aqueous Solutions" that alcohols are
covalent compounds that dissolve in water to give solutions of neutral molecules. Thus alcohols
are nonelectrolytes.
B The only solute species in solution is therefore (CH 3) 2CHOH molecules, so [(CH 3) 2CHOH] = 3.7 M.
c. A Indium nitrate is an ionic compound that contains In 3+ ions and NO 3− ions, so we expect
it to behave like a strong electrolyte in aqueous solution:
In(NO 3 ) 3 (s) → H 2 O(l) In 3+ (aq) + 3NO 3 – (aq)
B One formula unit of In(NO 3) 3 produces one In 3+ ion and three NO 3− ions, so a 0.032 M
In(NO 3) 3 solution contains 0.032 M In 3+ and 3 × 0.032 M = 0.096 M NO 3– —that is, [In 3+ ] = 0.032 M
and [NO 3− ] = 0.096 M.
Exercise
What are the concentrations of all species derived from the solutes in these aqueous solutions?
a. 0.0012 M Ba(OH) 2
b. 0.17 M Na 2SO 4
c. 0.50 M (CH 3) 2CO, commonly known as acetone
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