The Properties of Mixtures: Solutions and Colloids

Which would you expect to be more effective as soap, sodium acetate, or sodium stearate? Explain.

Hexane and methanol are miscible as gases but only slightly soluble in each other as liquids. Explain.

Which gives the more concentrated solution, 

(a)${\mathbf{KNO}}_{\mathbf{3}}$ In  ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}$or

(b) ${\mathbf{KNO}}_{\mathbf{3}}$ in carbon tetrachloride $\left({\mathbf{CCl}}_{\mathbf{4}}\right)$? Explain.

Which gives the more concentrated solution, stearic acid $\left[{\mathbf{CH}}_{\mathbf{3}}{\left({\mathbf{CH}}_{\mathbf{2}}\right)}_{\mathbf{16}}\mathbf{COOH}\right]$  in

a) ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}$  or

 b) ${\mathbf{CCl}}_{\mathbf{4}}$ ? Explain.

What is the strongest type of intermolecular force between

solute and solvent in each solution?

(a) $\mathbf{CsCl}\left(\mathbf{s}\right)$ in ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}\left(\mathbf{l}\right)$

(b) ${\mathbf{CH}}_{\mathbf{3}}{\mathbf{COCH}}_{\mathbf{3}}\left(\mathbf{l}\right)$ in ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}\left(\mathbf{l}\right)$

(c) ${\mathbf{CH}}_{\mathbf{3}}\mathbf{OH}\left(\mathbf{l}\right)$ in ${\mathbf{CCl}}_{\mathbf{4}}\left(\mathbf{l}\right)$

What is the strongest type of intermolecular force between solute and solvent in each solution?

1. ${\mathbf{CH}}_{\mathbf{3}}{\mathbf{OCH}}_{\mathbf{3}}\left(\mathbf{g}\right){\mathbf{inH}}_{\mathbf{2}}\mathbf{O}\left(\mathbf{l}\right)$
   
2. $\mathbf{Ne}\left(\mathbf{g}\right){\mathbf{inH}}_{\mathbf{2}}\mathbf{O}\left(\mathbf{l}\right)$
   
3. ${\mathbf{N}}_{\mathbf{2}}\left(\mathbf{g}\right){\mathbf{inC}}_{\mathbf{4}}{\mathbf{H}}_{\mathbf{10}}\left(\mathbf{g}\right)$
   

What is the strongest type of intermolecular force between solute and solvent in each solution?

1. ${\mathbf{C}}_{\mathbf{6}}{\mathbf{H}}_{\mathbf{14}}\left(\mathbf{l}\right){\mathbf{inC}}_{\mathbf{8}}{\mathbf{H}}_{\mathbf{18}}\left(\mathbf{l}\right)$
   
2. ${\mathbf{H}}_{\mathbf{2}}\mathbf{C}\mathbf{=}\mathbf{O}\left(\mathbf{g}\right){\mathbf{inCH}}_{\mathbf{3}}\mathbf{OH}\left(\mathbf{l}\right)$
   
3. ${\mathbf{Br}}_{\mathbf{2}}{\mathbf{inCCl}}_{\mathbf{4}}\left(\mathbf{l}\right)$
   

Which member of each pair is more soluble in diethyl ether? Why?

1. $\mathbf{NaCl}\left(\mathbf{s}\right)\mathbf{orHCl}\left(\mathbf{g}\right)$
2. ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}\left(\mathbf{l}\right)\mathbf{orMeCHO}\left(\mathbf{l}\right)$
3. ${\mathbf{MgBr}}_{\mathbf{2}}\left(\mathbf{s}\right)\mathbf{ }\mathbf{or}\mathbf{ }{\mathbf{CH}}_{\mathbf{3}}{\mathbf{CH}}_{\mathbf{2}}\mathbf{MgBr}\left(\mathbf{s}\right)$
   

Question: what type of intermolecular forces give rise to hydration shells in an aqueous solution of sodium chloride.

Question: Acetic acid is miscible with water. Would you expect carboxylic acids with the general formula ${\mathbf{CH}}_{\mathbf{3}}{\left({\mathbf{CH}}_{\mathbf{2}}\right)}_{\mathbf{n}}\mathbf{COOH}$ to become more or less water-soluble as n increases? Explain.

Question: Describe how the properties of seawater illustrate the two characteristics that define mixtures.

Which member of each pair is more soluble in water? Why?

1. ${\mathbf{CH}}_{\mathbf{3}}{\mathbf{CH}}_{\mathbf{2}}{\mathbf{OCH}}_{\mathbf{2}}{\mathbf{CH}}_{\mathbf{3}}\left(\mathbf{l}\right)\mathbf{ }\mathbf{or}\mathbf{ }{\mathbf{CH}}_{\mathbf{3}}{\mathbf{CH}}_{\mathbf{2}}{\mathbf{OCH}}_{\mathbf{3}}\left(\mathbf{g}\right)$
   
2. ${\mathbf{CH}}_{\mathbf{2}}{\mathbf{Cl}}_{\mathbf{2}}\left(\mathbf{l}\right)\mathbf{ }\mathbf{or}\mathbf{ }\mathbf{ }{\mathbf{CCl}}_{\mathbf{4}}\mathbf{\left(}\mathbf{l}\mathbf{\right)}$
   
3. 
   

The dictionary defines homogenous as “uniform in composition throughout.” River water is a mixture of dissolved compounds, such as calcium bicarbonate, and suspended soil particles. Is river water homogenous? Explain.

Gluconic acid is a derivative of glucose used in cleaners and in the dairy and brewing industries. Caproic acid is a carboxylic acid used in the flavouring industry. Although both are six-carbon acids (see structures below), gluconic acid is soluble in water and nearly soluble in hexane, whereas caproic acid has the composite solubility behaviour. Explain.

Name three intermolecular forces that stabilize the shape of a soluble, globular protein, and explain how they act.

Name three intermolecular forces that stabilize the shape of DNA, and explain how they act.

Is the sodium salt of propanoic acid as effective as soap as sodium stearate? Explain.

What intermolecular forces stabilize a lipid bilayer?

Question:  What is the relation between hydration and solvation?

Question:  Histones are proteins that control gene function by attaching through salt links to exterior regions of DNA. Name an amino acid whose side chain is often found on the exterior of histones

Question: How can wood be so strong if it consists of cellulose chains held together by relatively weak H bonds?

Question: In what way do proteins embedded in a membrane differ structurally from soluble proteins?

Question: Hydrogen chloride (HCl) gas is much more soluble than propane gas  in water, even though HCl has a lower boiling point. Explain.

For  ${\mathbf{\Delta H}}_{\mathbf{solution}}$ to be very small, what quantities must be nearly equal in magnitude? Will their signs be the same or opposite? 

An ionic compound has a highly negative ${\mathbf{\Delta H}}_{\mathbf{soln}}$ in water. Would you expect it to be very soluble or nearly soluble or nearly insoluble in water? Explain in terms of enthalpy and entropy changes.

You are given a bottle of solid X and three aqueous solutions of X—one saturated, one unsaturated, and one supersaturated. How would you determine which solution is which?

Potassium permanganate (${\mathbf{KMnO}}_{\mathbf{4}}$ ) has a solubility of 6.4 g/100 g of  ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}$ at ${\mathbf{20}}^{\mathbf{o}}\mathbf{C}$  and a curve of solubility vs. temperature that slopes upward to the right. How would you prepare a supersaturated solution of  ${\mathbf{KMnO}}_{\mathbf{4}}$?

Why does the solubility of any gas in water decrease with rising temperature?

Respiratory problems are treated with devices that deliver air with a higher partial pressure of  ${\text{O}}_{\text{2}}$ than normal air. Why?

Explain the difference between molarity and molality. Under what circumstances would molality be a more accurate measure of the concentration of a prepared solution than molarity? Why?

Which way of expressing concentration includes

1. volume of solution;
2. mass of solution;
3. mass of solvent?

A solute has a solubility in water of  $\mathbf{21}\mathbf{g}\mathbf{/}\mathbf{kg}$ solvent. Is this value the same as $\mathbf{21}\mathbf{g}\mathbf{/}\mathbf{kg}$  solution? Explain.

You want to convert among molarity, molality, and mole fraction of a solution. You know the masses of solute and solvent and the volume of solution. Is this enough information to carry out all the conversions? Explain.

The Henry’s law constant (k_H) for ${\mathbf{O}}_{\mathbf{2}}$  in water at ${\mathbf{20}}^{\mathbf{o}}\mathbf{C}$  in $\mathbf{1}\mathbf{.}\mathbf{28}\mathbf{\times }{\mathbf{10}}^{\mathbf{-}\mathbf{3}}{\mathbf{molL}}^{\mathbf{-}\mathbf{1}}{\mathbf{atm}}^{\mathbf{-}\mathbf{1}}$ .

(a) How many grams of  ${\mathbf{O}}_{\mathbf{2}}$ will dissolve in 2.50 L of ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}$  that is in contact with pure ${\mathbf{O}}_{\mathbf{2}}$  at 1.00 atm?

(b) How many grams of ${\mathbf{O}}_{\mathbf{2}}$ will dissolve in 2.50 L of  ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}$ that is in contact with air, where the partial pressure of is 0.209 atm?

For a saturated aqueous solution of each of the following at   and 1atm, will the solubility increase, decrease, or stay the same when the indicated change occurs?

 (a)He(g), decrease T

 (b)RbI(s), increase P

For a saturated aqueous solution of each of the following at  ${\mathbf{20}}^{\mathbf{o}}\mathbf{C}$ and 1atm, will the solubility increase, decrease, or stay the same when the indicated change occurs?

(a) ${\mathbf{O}}_{\mathbf{2}}\left(\mathbf{g}\right)$, increase P

(b) ${\mathbf{N}}_{\mathbf{2}}\left(\mathbf{g}\right)$, increase V

For a saturated aqueous solution of each of the following at ${\mathbf{20}}^{\mathbf{o}}\mathbf{C}$  and 1atm, will the solubility increase, decrease, or stay the same when the indicated change occurs?

(a) ${\mathbf{O}}_{\mathbf{2}}\left(\mathbf{g}\right)$, increase P

(b)${\mathbf{N}}_{\mathbf{2}}\left(\mathbf{g}\right)$ , increase V

The partial pressure of  ${\mathbf{CO}}_{\mathbf{2}}$ gas above the liquid in a bottle of champagne at ${\mathbf{20}}^{\mathbf{o}}\mathbf{C}$ is 5.5 atm. What is the solubility of  ${\mathbf{CO}}_{\mathbf{2}}$ in champagne? Assume Henry’s law constant is the same for champagne as for water: at ${\mathbf{20}}^{\mathbf{o}}\mathbf{C}$ , $\mathbf{KH}\mathbf{=}\mathbf{3}\mathbf{.}\mathbf{7}\mathbf{\times }{\mathbf{10}}^{\mathbf{-}\mathbf{2}}\mathbf{mol}\text{/}\mathbf{L}·\mathbf{atm}$ .

When a solution is heated, which ways of expressing concentration change in value? Which remain unchanged? Explain.

Question: Water is added to a flask containing solid . As the salt dissolves, the solution becomes colder.

(a) Is the dissolving of NH₄CI  exothermic or endothermic? 

(b) Is the magnitude of$\mathit{\Delta }{\mathit{H}}_{\mathbf{l}\mathbf{a}\mathbf{t}\mathbf{t}\mathbf{i}\mathbf{c}\mathbf{e}}$  of  larger or smaller than the combined $\mathit{\Delta }{\mathit{H}}_{\mathbf{hydro}}$ of the ions? 

(c) Given the answer to (a), why does NH₄CI dissolve in water.

Question: (a) What is the charge density of an ion, and what two properties of an ion affect it? 

(b) Arrange the following in order of increasing charge density: $\left(+\left)\right(-\left)\right(2^{-}\left)\right(3^{+}\right)$

(c) How do the properties in part (a) affect the ionic heat of hydration,$\mathit{\Delta }{\mathit{H}}_{\mathbf{\text{Hydration}}}$ ?

Question: For a general solvent, which enthalpy terms in the thermochemical solution cycle are combined to obtain  $\Delta H_{solvation}$?

Caffeine is about 10 times as soluble in hot water as in cold water. A chemist puts a hot-water extract of caffeine into an ice bath, and some caffeine crystallizes. Is the remaining solution saturated, unsaturated, or supersaturated?

Calculate the molarity of each aqueous solution: 

1. 32.3 g of table sugar ( ${\mathbf{C}}_{\mathbf{12}}{\mathbf{H}}_{\mathbf{22}}{\mathbf{O}}_{\mathbf{11}}$) in 100. mL of solution 
2. 5.80 g of ${\mathbf{LiNO}}_{\mathbf{3}}$ in 505 mL of solution.

Calculate the molarity of each aqueous solution:

1.   0.82 g of ethanol (${\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{5}}\mathbf{OH}$ ) in 10.5 mL of solution
2. 1.27 g of gaseous  ${\mathbf{NH}}_{\mathbf{3}}$ in 33.5 mL of solution.

Calculate the molarity of each aqueous solution: 

(a) 78.0 mL of 0.240 M NaOH diluted to 0.250 L with water.

(b) 38.5 mL of 1.2 M ${\mathbf{HNO}}_{\mathbf{3}}$  diluted to 0.130 L with water.

Calculate the molarity of each aqueous solution: 

(a) 25.5 mL of 6.25 M HCl diluted to 0.500 L with water 

(b) 8.25 mL of $\mathbf{2}\mathbf{.}\mathbf{00}\mathbf{\times }{\mathbf{10}}^{\mathbf{-}\mathbf{2}}\mathbf{M}$ KI diluted to 12.0 mL with water

How would you prepare the following aqueous solutions? 

(a) 365 mL of  $\mathbf{8}\mathbf{.}\mathbf{55}\mathbf{\times }{\mathbf{10}}^{\mathbf{-}\mathbf{2}}\mathbf{M}$  ${\mathbf{KH}}_{\mathbf{2}}{\mathbf{PO}}_{\mathbf{4}}$ from solid  ${\mathbf{KH}}_{\mathbf{2}}{\mathbf{PO}}_{\mathbf{4}}$

(b) 465 mL of 0.335 M NaOH from 1.25 M NaOH.

How would you prepare the following aqueous solutions? 

(a) 2.5 L of 0.65 M NaCl from solid NaCl 

(b) 15.5 L of 0.3 M urea $\mathbf{[}{\left({\mathbf{NH}}_{\mathbf{2}}\right)}_{\mathbf{2}}\mathbf{C}\mathbf{=}\mathbf{O}\mathbf{]}$ from 2.1 M urea.

How would you prepare the following aqueous solutions? 

(a) 1.40 L of 0.288 M KBr from solid KBr 

(b) 255 mL of 0.0856 M  ${\mathbf{LiNO}}_{\mathbf{3}}$ from 0.264 M ${\mathbf{LiNO}}_{\mathbf{3}}$ .