Question 4.4: calculating the concentration of Ions in a Solution What is ...
calculating the concentration of Ions in a Solution
What is the total molar concentration of ions in a 0.350 M solution of the strong electrolyte Na_{2}SO_{4} , assuming complete dissociation?
IDENTIFY
| Known | Unknown | ||
| Molar concentration of compound (0.350 M Na_{2}SO_{4}) |
Total molar concentration of ions |
STRATEGY
The ions come from the dissociation of Na_{2}SO_{4} , and therefore a reaction for dissolving Na_{2}SO_{4} in water is written. The balanced reaction shows that 3 mol of ions are formed from 1 mol of the compound: 2 mol of Na^{+} and 1 mol of SO^{2-}_{4}.
Na_{2}SO_{4}(s)\overset{H_{2}O}{\longrightarrow }2 Na^{+}(aq) + SO^{2-}_{4}(aq)
Assuming complete dissociation, the total molar concentration of ions is three times the molarity of Na_{2}SO_{4}, or 1.05 M:
\frac{0.350 \cancel{ mol Na_{2}SO_{4}}}{1 L}\times \frac{3 mol ions }{1 \cancel{ mol Na_{2}SO_{4}}}=1.05 M