7.19.2: Answers to Solutions (Exercises)
- Page ID
- 291717
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)
( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\id}{\mathrm{id}}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\kernel}{\mathrm{null}\,}\)
\( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\)
\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\)
\( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)
\( \newcommand{\vectorA}[1]{\vec{#1}} % arrow\)
\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}} % arrow\)
\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vectorC}[1]{\textbf{#1}} \)
\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)
\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)
\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
Water, Solutions, & Electrolytes
1. (a) true; (b) false; (c) false; (d) true
2. (I) c (II) b (III) a
3. (a) heptane; (b) water; (c) water
4. Crystals of NaCl dissolve in water, a polar liquid with a very large dipole moment, and the individual ions become strongly solvated. Hexane is a nonpolar liquid with a dipole moment of zero and, therefore, does not significantly interact with the ions of the NaCl crystals.
5. HBr is an acid and so its molecules react with water molecules to form H3O+ and Br− ions that provide conductivity to the solution. Though HBr is soluble in benzene, it does not react chemically but remains dissolved as neutral HBr molecules. With no ions present in the benzene solution, it is electrically nonconductive.
6.
(a) high conductivity (solute is an ionic compound that will dissociate when dissolved)
(b) high conductivity (solute is a strong acid and will ionize completely when dissolved)
(c) nonconductive (solute is a covalent compound, neither acid nor base, unreactive towards water)
(d) low conductivity (solute is a weak base and will partially ionize when dissolved)
7. (a) true (b) false (c) false (d) true (e) false
8. (a) molecule (b) electrolyte (c) molecule (d) electrolyte
9.
(a) solute: CO2; solvent: water
(b) solute: NaCl; solvent: water
(c) solute: C12H22O11 (sucrose); solvent: water
(d) solute: NaHCO3 (baking soda); solvent: water
(e) solute: O2; solvent: N2
Solubility
1. Solubility is the amount of a solute that can dissolve in a given amount of solute, typically 100 mL. The solubility of solutes varies widely.
2.
a. ~100C
b. ~ 30 grams of NaBr
c. unsaturated
d. 90 grams of KNO3
e. The KBr solution is saturated since the amount of water is only 50 grams. Therefore, the saturation point at 200C is 33 grams of KBr in 50 grams of water.
f. ~25 grams of NaNO3 would precipitate out.
3. a
Concentration
1.The term dilute means relatively less solute and the term concentrated implies relatively more solute. Both are of limited usefulness because these are not accurate.
2. a. 26.5% NaCl m/m% solution b. 2.15% MgCO3 m/m% solution
3. 1.34% C6H6 v/v% solution
4. 3.4% C6H5NH2 v/v% solution
5. 52.4 mL C2H5OH
6. 5.18 g
7. 0.00321 g
8. 2.57 x 10-4 g
9. 15 ppm
10. 7,580,000 ppb
11. 0.130 M
12. 0.0458 M
13. 0.36 M
14. 3.52 M
Precipitates
1.
a. 2PO43-(aq) + 3Ca2+ (aq) → Ca3(PO4)2(s)
b. Ba2+(aq) + SO42-(aq) → BaSO4(s)
c. Ag+(aq) + Cl- → AgCl(s)
2.
a. Molecular: Pb(NO3)2(aq) + 2KI(aq) → PbI2(s) + 2KNO3(aq)
Ionic: Pb2+(aq) + 2NO3-(aq) + 2K+(aq) + 2I-(aq) → PbI2(s) + 2K+(aq) + 2NO3-(aq)
Net Ionic: Pb2+(aq) + 2I-(aq) → PbI2(s)
b. no precipitate forms (no reaction)
c. Molecular: CaCl2(aq) + Na2CO3(aq) → 2NaCl(aq) + CaCO3(s)
Ionic: Ca+2(aq) + 2Cl−1(aq) + 2Na+1(aq) + CO3−2(aq) → 2Na+1(aq) + 2Cl−1(aq) + CaCO3(s)
Net Ionic: Ca+2(aq) + CO3−2(aq) → CaCO3(s)