4.7 Stoichiometry of Reactions in Aqueous Solutions
- Page ID
- 166326
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Stoichiometry in Solutions
Exercise \(\PageIndex{1}\)
The concentration of sulfate in a sample of wastewater is to be determined by using gravimetric analysis. To a 100.0-mL sample of the wastewater is added an excess of barium nitrate, forming the insoluble barium sulfate (233.4 g/mol) according to the balanced equation given below. The solid barium sulfate is dried, and its mass is measured to be 0.9951 g. What was the concentration of sulfate in the original wastewater sample?
SO42–(aq) + Ba(NO3)2(aq) → BaSO4(s) + 2NO3–(aq)
- Answer
-
\(n_{BaSO_{4}}=\frac{0.9951g BaSO_{4}}{233.4 g/mol}=4.265 * 10^{-3} M\)
Exercise \(\PageIndex{2}\)
Zn reacts with hydrochloric acid.
Zn(s) + 2 HCl(aq) → ZnCl2(aq) + H2(g)
What volume of 3.05 M HCl(aq) will react with 25.0 g Zn(s)?
- Answer
-
0.251 L
Exercise \(\PageIndex{3}\)
What minimum mass of cobalt (II) nitrate must be added to 60.0 mL of a 0.0999 M phosphate solution in order to completely precipitate all of the phosphate as solid cobalt (II) phosphate?
2PO43–(aq) + 3Co(NO3)2(aq) → Co3(PO4)2(s) + 6NO3–(aq)
- Answer
-
1.64 g
Titrations
Exercise \(\PageIndex{4}\)
The reaction of HCl with NaOH is represented by the equation
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
What volume of 0.614 M HCl is required to titrate 18.8 mL of 0.619 M NaOH?
- Answer
-
19.0 mL
\(V_{HCl}=V_{NaOH}\left ( \frac{M_{NaOH}}{M_{HCl}} \right )=18.8*\left ( \frac{0.619 M}{0.614 M} \right )=18.95 mL\)
Exercise \(\PageIndex{5}\)
What volume of 0.955 M HCl, in milliliters, is required to titrate 2.152 g of Na2CO3 to the equivalence point?
Na2CO3(aq) + 2 HCl(aq) → H2O(ℓ) + CO2(g) + 2 NaCl(aq)
- Answer
-
42.5 mL HCl
\(moles Na_{2}CO_{3}=\frac{2.152g}{105.98844g/mol}=0.0203 moles Na_{2}CO_{3}\)
\[moles HCl = 2*0.0203=0.0406 moles HCl\]
\[V=\frac{0.0406 moles HCl}{0.955 M}=0.0425 L= 42.5 mL\]

