Exercises
- Page ID
- 54340
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Section 6-1
Q6-1
What is a solution?
Q6-2
Please give an example of a solution
Q6-3
How do you know it is a solution (and not a mixture)?
Q6-4
When something dissolves, what happens to it?
Q6-5
If you add 5 g of salt to 100g of water and allow it to dissolve, what is the resulting mass?
Section 6-2
Q6-1
Please define:
A) solute
B) solvent
C) concentration
Q6-2
A) If you have 200 mL of a 1.5 M solution of glucose (C6H12O6), how many moles of glucose are in the solution?
B) What mass of glucose is in that volume of solution?
C) If you needed a 0.050 M solution of glucose, and you only had the solution in 2a, what would you do?
D) If you needed a 0.050 M solution of glucose, and you only had the solution in 2a, what would you do?
Q6-3
How would you prepare 100 mL of a 0.15 M solution of sodium chloride?
Section 6-3
Q6-1
Draw the Lewis structure for ethanol CH3CH2OH
Q6-2
What intermolecular forces are present in ethanol? Explain why you think they are present.
Q6-3
If ethanol dissolves in water what interactions would be present between the water molecules and the ethanol molecules? Draw a representation showing the interactions.
Q6-4
If ethanol dissolves in water, which changes would require an energy input from the surroundings? Which would produce energy?
Section 6-4
Here is the table from the text:
|
Compound |
Molar mass (g/mol) |
Structure |
Solubility (g/L) 20 ºC |
|
Propane |
44 |
CH3CH2CH3 |
0.07g/L |
|
Ethanol |
46 |
CH3CH2OH |
Completely miscible |
|
Dimethyl ether |
46 |
CH3OCH3 |
328 g/L |
|
Pentane |
72 |
CH3CH2CH2CH2CH3 |
0.4 g/L |
|
Butanol |
74 |
CH3CH2CH2CH2OH |
80 g/L |
|
Diethyl ether |
74 |
CH3CH2OCH2CH3 |
69 g/L |
|
hexanol |
102 |
CH3CH2CH2CH2CH2CH2CH2OH |
0.4 g/L |
|
1,6 hexanediol |
226 |
HOCH2CH2CH2CH2CH2CH2CH2OH |
500 g/L |
|
Glucose |
180 |
C6H12O6 |
910g/L |
Q6-1
How do you distinguish which compounds are soluble or insoluble, is it a “yes/no” question?
Q6-2
Which of these compounds would you say are soluble in water?
Q6-3
Draw a Lewis structures for propane, ethanol, and dimethyl ether.
Q6-4
What possible interactions are there between the solute and solvent for each substance? Draw them.
Q6-5
Do the types of interactions allow you to predict relative solubilities?
Section 6-5
Q6-1
You make a solution using a solid solute (5g) in water (total volume 100 mL). The molar mass of the solute is 110 g/mol
A) What is the molarity?
B) What is the concentration reported as % by mass? (assuming the density of water is 1g/mL)
C) What is different about these two concentration units? (why would you use one rather than another?)
Q6-2
When you make the solution, all the solute dissolves and the temperature rises, what does that allow you to say about:
A) ΔG for solution
B) ΔH for solution
C) ΔS for solution
D) The relative strengths of the interactions before mixing (solute-solute, and solvent-solvent), and after mixing (solute-solvent)
Section 6-6
Q6-1
What kind of bonding is present in CaCl2? (How do you know?)
Q6-2
Draw a picture of CaCl2 solid. Be sure to take into consideration how it looks (size and the relationship between Ca and Cl).
Q6-3
CaCl2 is soluble in water. Draw a picture of what the solution might look like, showing water molecules, the Ca and the Cl species.
Q6-4
What property does a solution of CaCl2 have that a solution of sugar does not? (It may help if you draw what an aqueous solution of sugar would look like.) How could you test your predictions?
Section 6-7
Q6-1
A) Take the first baggie, which contains CaCl2, and add a few drops of water to the white power. What happens? Record your observations.
|
Is thermal energy released from, or absorbed by the system? |
What is the sign of ΔG for this process? How do you know? |
What is the sign of ΔH for this process? How do you know |
What is the sign of ΔS for this process? How do you know |
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B) What do you think is happening? Why is there a temperature change? Does this explain why the white powder is soluble?
Q6-2
A) Now take the second baggie (which contains NH4Cl) and repeat. Record your observations.
|
Is thermal energy released from, or absorbed by the system? |
What is the sign of ΔG for this process? How do you know? |
What is the sign of ΔH for this process? How do you know |
What is the sign of ΔS for this process? How do you know |
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Q6-3
In light of your observations – what thermodynamic factors do you think are important to understand for the process of solubility?
Section 6-8
For each solute, and solvent indicate what interactions are present, what interactions are present between the solute and solvent in solution. (draw structures showing interactions)
|
Solute |
Solvent |
Solution |
|
CH3OH
|
H2O |
|
|
CH3OH
|
CH3COOH
|
|
|
CaCl2
|
H2O
|
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|
NH4Cl
|
H2O |
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CaCl2 |
Hexane (C6H14)
|
|
Section 6-9
For each of the following solutions use the experimental evidence given to predict what happens when the solvent is mixed with the solute.
Q6-1
CH3OH is completely soluble in water in all proportions: when they mix the temperature increases. Predict the sign of ΔH, ΔS and ΔG, and explain your reasoning by drawing molecular level pictures
Q6-2
The solubility of NaCl is 359 g/L at 298K. When it dissolves the temperature drops. Predict the sign of ΔH, ΔS and ΔG, and explain your reasoning by drawing molecular level pictures.
Q6-3
Calcium phosphate (Ca3(PO4)2) is insoluble in water. The ΔH for solution is about zero. Predict the signs of ΔS and ΔG, and explain your reasoning by drawing molecular level pictures