Chemistry

Paul Flowers, Klaus Theopold, Richard Langley

Chapter 11

Solutions and Colloids - all with Video Answers

Educators

Chapter Questions

Problem 1

How do solutions differ from compounds? From other mixtures?

Aadit Sharma

Aadit Sharma

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Problem 2

Which of the principal characteristics of solutions are evident in the solt shown in Figure 11.2?

Bhumika Jayee

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Problem 3

When $\mathrm{KNO}_{3}$ is dissolved in water, the resulting solution is significantly colder than the water was originally.
(a) Is the dissolution of $\mathrm{KNO}_{3}$ an endothermic or an exothermic process?
(b) What conclusions can you draw about the intermolecular attractions involved in the process?
(c) Is the resulting solution an ideal solution?

Aadit Sharma

Numerade Educator

Problem 4

Give an example of each of the following types of solutions:
(a) a gas in a liquid
(b) a gas in a gas
(c) a solid in a solid

Rikhil Makwana

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Problem 5

Indicate the most important types of intermolecular attractions in each of the following solutions:
(a) The solution in Figure $11.2 .$
(b) $\mathrm{NO}()$ in $\mathrm{CO}(\mathrm{l})$
(c) $\mathrm{Cl}_{2}(g)$ in $\mathrm{Br}_{2}(l)$
(d) HCI( $g$ ) in benzene $C_{6} \mathrm{H}_{6}(l)$
(e) Methanol CH $_{3}$ OH () in $\mathrm{H}_{2} \mathrm{O}(I)$

Bhumika Jayee

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Problem 6

Predict whether each of the following substances would be more soluble in water (polar solvent) or in a hydrocarbon such as heptane (C $_{7} \mathrm{H}_{16}$, nonpolar solvent):
(a) vegetable oil (nonpolar)
(b) isopropyl alcohol (polar)
(c) potassium bromide (ionic)

Rikhil Makwana

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Problem 7

Heat is released when some solutions form; heat is absorbed when other solutions form. Provide a molecular explanation for the difference between these two types of spontaneous processes.

Aadit Sharma

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Problem 8

Solutions of hydrogen in palladium may be formed by exposing Pd metal to $\mathrm{H}_{2}$ gas. The concentration of hydrogen in the palladium depends on the pressure of $\mathrm{H}_{2}$ gas applied, but in a more complex fashion than can be described by Henry's law. Under certain conditions, 0.94 g of hydrogen gas is dissolved in 215 g of palladium metal (solution density $=10.8 \mathrm{g} \mathrm{cm}^{3}$ ).
(a) Determine the molarity of this solution.
(b) Determine the molality of this solution.
(c) Determine the percent by mass of hydrogen atoms in this solution.

Rikhil Makwana

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Problem 9

Explain why the ions $\mathrm{Na}^{+}$ and $\mathrm{Cl}^{-}$ are strongly solvated in water but not in hexane, a solvent composed of nonpolar molecules.

Bhumika Jayee

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Problem 10

Explain why solutions of HBr in benzene (a nonpolar solvent) are nonconductive, while solutions in water (a polar solvent) are conductive.

Rikhil Makwana

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Problem 11

Consider the solutions presented:
(a) Which of the following sketches best represents the ions in a solution of $\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3}(a q) ?$
(b) Write a balanced chemical equation showing the products of the dissolution of $\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3}$

Aadit Sharma

Numerade Educator

Problem 12

Compare the processes that occur when methanol (CH $_{3}$ OH), hydrogen chloride (HCl), and sodium hydroxide (NaOH) dissolve in water. Write equations and prepare sketches showing the form in which each of these compounds is present in its respective solution.

Bhumika Jayee

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Problem 13

What is the expected electrical conductivity of the following solutions?
(a) $\mathrm{NaOH}(a q)$
(b) HCl( $a q$ )
(c) $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(a q)$ (glucose)
(d) $\mathrm{NH}_{3}(a q)$

Aadit Sharma

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Problem 14

Why are most solid ionic compounds electrically nonconductive, whereas aqueous solutions of ionic compounds are good conductors? Would you expect a liquid (molten) ionic compound to be electrically conductive or nonconductive? Explain.

Rikhil Makwana

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Problem 15

Indicate the most important type of intermolecular attraction responsible for solvation in each of the following solutions:
(a) the solutions in Figure 11.7
(b) methanol, CH $_{3}$ OH, dissolved in ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$
(c) methane, CH_ dissolved in benzene, $\mathbf{C}_{\mathbf{6}} \mathbf{H}_{\mathbf{6}}$
(d) the polar halocarbon $\mathrm{CF}_{2} \mathrm{Cl}_{2}$ dissolved in the polar halocarbon $\mathrm{CF}_{2} \mathrm{ClCFCl}_{2}$
(e) $\mathrm{O}_{2}()$ in $\mathrm{N}_{2}($ )

Bhumika Jayee

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Problem 16

Suppose you are presented with a clear solution of sodium thiosulfate, $\mathrm{Na}_{2} \mathrm{S}_{2} \mathrm{O}_{3}$. How could you determine whether the solution is unsaturated, saturated, or supersaturated?

Rikhil Makwana

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Problem 17

Supersaturated solutions of most solids in water are prepared by cooling saturated solutions. Supersaturated solutions of most gases in water are prepared by heating saturated solutions. Explain the reasons for the difference in the two procedures.

Aadit Sharma

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Problem 18

Suggest an explanation for the observations that ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$, is completely miscible with water and that ethanethiol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{SH},$ is soluble only to the extent of $1.5 \mathrm{g}$ per $100 \mathrm{mL}$ of water.

Rikhil Makwana

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Problem 19

Calculate the percent by mass of KBr in a saturated solution of KBr in water at $10^{\circ} \mathrm{C}$. See Figure 11.16 for useful data, and report the computed percentage to one significant digit.

Aadit Sharma

Numerade Educator

Problem 20

Which of the following gases is expected to be most soluble in water? Explain your reasoning.
(a) $\mathrm{CH}_{4}$
(b) $\mathrm{CCl}_{4}$
(c) $\mathrm{CHCl}_{3}$

Rikhil Makwana

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Problem 21

At $0^{\circ} \mathrm{C}$ and 1.00 atm, as much as $0.70 \mathrm{g}$ of $\mathrm{O}_{2}$ can dissolve in 1 L of water. At $0^{\circ} \mathrm{C}$ and 4.00 atm, how many grams of $\mathrm{O}_{2}$ dissolve in 1 L of water?

Aadit Sharma

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Problem 22

Refer to Figure $11.10 .$
(a) How did the concentration of dissolved $\mathrm{CO}_{2}$ in the beverage change when the bottle was opened?
(b) What caused this change?
(c) Is the beverage unsaturated, saturated, or supersaturated with $\mathrm{CO}_{2}$ ?

Rikhil Makwana

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Problem 23

The Henry's law constant for $\mathrm{CO}_{2}$ is $3.4 \times 10^{-2} \mathrm{M} / \mathrm{atm}$ at $25^{\circ} \mathrm{C}$. Assuming ideal solution behavior, what pressure of carbon dioxide is needed to maintain a $\mathrm{CO}_{2}$ concentration of $0.10 \mathrm{M}$ in a can of lemon-lime soda?

Bhumika Jayee

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Problem 24

The Henry's law constant for $\mathrm{O}_{2}$ is $1.3 \times 10^{-3} \mathrm{M} /$ atm at $25^{\circ} \mathrm{C}$. Assuming ideal solution behavior, what mass of oxygen would be dissolved in a 40-L aquarium at $25^{\circ} \mathrm{C}$, assuming an atmospheric pressure of $1.00 \mathrm{atm}$, and that the partial pressure of $\mathrm{O}_{2}$ is 0.21 atm?

Bhumika Jayee

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Problem 25

Assuming ideal solution behavior, how many liters of HCl gas, measured at 30.0 ^ C and 745 torr, are required to prepare 1.25 L of a 3.20-M solution of hydrochloric acid?

Ronald Prasad

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Problem 26

Which is/are part of the macroscopic domain of solutions and which is/are part of the microscopic domain:
boiling point elevation, Henry's law, hydrogen bond, ion-dipole attraction, molarity, nonelectrolyte, nonstoichiometric compound, osmosis, solvated ion?

Bhumika Jayee

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Problem 27

What is the microscopic explanation for the macroscopic behavior illustrated in Figure $11.14 ?$

Aadit Sharma

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Problem 28

Sketch a qualitative graph of the pressure versus time for water vapor above a sample of pure water and a sugar solution, as the liquids evaporate to half their original volume.

Rikhil Makwana

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Problem 29

A solution of potassium nitrate, an electrolyte, and a solution of glycerin $\left(\mathrm{C}_{3} \mathrm{H}_{5}(\mathrm{OH})_{3}\right),$ a nonelectrolyte, both boil at $100.3^{\circ} \mathrm{C} .$ What other physical properties of the two solutions are identical?

Aadit Sharma

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Problem 30

What are the mole fractions of $\mathrm{H}_{3} \mathrm{PO}_{4}$ and water in a solution of $14.5 \mathrm{g}$ of $\mathrm{H}_{3} \mathrm{PO}_{4}$ in $125 \mathrm{g}$ of water?
(a) Outline the steps necessary to answer the question.
(b) Answer the question.

Rikhil Makwana

Numerade Educator

Problem 31

What are the mole fractions of $\mathrm{HNO}_{3}$ and water in a concentrated solution of nitric acid $\left(68.0 \% \mathrm{HNO}_{3} \mathrm{by}\right.$ mass)?
(a) Outline the steps necessary to answer the question.
(b) Answer the question.

Aadit Sharma

Numerade Educator

Problem 32

Calculate the mole fraction of each solute and solvent:
(a) $583 \mathrm{g}$ of $\mathrm{H}_{2} \mathrm{SO}_{4}$ in $1.50 \mathrm{kg}$ of water $-$ the acid solution used in an automobile battery
(b) $0.86 \mathrm{g}$ of $\mathrm{NaCl}$ in $1.00 \times 10^{2} \mathrm{g}$ of water $-$ a solution of sodium chloride for intravenous injection
(c) $46.85 \mathrm{g}$ of codeine, $\mathrm{C}_{18} \mathrm{H}_{21} \mathrm{NO}_{3}$, in $125.5 \mathrm{g}$ of ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$
(d) $25 \mathrm{g}$ of $\mathrm{I}_{2}$ in $125 \mathrm{g}$ of ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$

Rikhil Makwana

Numerade Educator

Problem 33

Calculate the mole fraction of each solute and solvent:
(a) $0.710 \mathrm{kg}$ of sodium carbonate (washing soda), $\mathrm{Na}_{2} \mathrm{CO}_{3},$ in $10.0 \mathrm{kg}$ of water $-$ a saturated solution at $0^{\circ} \mathrm{C}$
(b) $125 \mathrm{g}$ of $\mathrm{NH}_{4} \mathrm{NO}_{3}$ in $275 \mathrm{g}$ of water $-$ a mixture used to make an instant ice pack
(c) 25 g of $\mathrm{Cl}_{2}$ in $125 \mathrm{g}$ of dichloromethane, $\mathrm{CH}_{2} \mathrm{Cl}_{2}$
(d) 0.372 g of tetrahydropyridine, C $_{5} \mathrm{H}_{9} \mathrm{N},$ in $125 \mathrm{g}$ of chloroform, $\mathrm{CHCl}_{3}$

Susan Hallstrom

Susan Hallstrom

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Problem 34

Calculate the mole fractions of methanol, $\mathrm{CH}_{3} \mathrm{OH} ;$ ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH} ;$ and water in a solution that is $40 \%$ methanol, 40\% ethanol, and 20\% water by mass. (Assume the data are good to two significant figures.)

Rikhil Makwana

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Problem 35

What is the difference between a 1 M solution and a 1 m solution?

Aadit Sharma

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Problem 36

What is the molality of phosphoric acid, $\mathrm{H}_{3} \mathrm{PO}_{4}$, in a solution of $14.5 \mathrm{g}$ of $\mathrm{H}_{3} \mathrm{PO}_{4}$ in $125 \mathrm{g}$ of water?
(a) Outline the steps necessary to answer the question.
(b) Answer the question.
37. What is the molality of nitric acid in a concentrated solution of nitric acid ( $68.0 \%$ HNO $_{3}$ by mass)?
(a) Outline the steps necessary to answer the question.
(b) Answer the question.

Bhumika Jayee

Numerade Educator

Problem 37

What is the molality of nitric acid in a concentrated solution of nitric acid (68.0\% HNO $_{3}$ by mass)?
(a) Outline the steps necessary to answer the question.
(b) Answer the question.

Aadit Sharma

Numerade Educator

Problem 38

Calculate the molality of each of the following solutions:
(a) $583 \mathrm{g}$ of $\mathrm{H}_{2} \mathrm{SO}_{4}$ in $1.50 \mathrm{kg}$ of water $-$ the acid solution used in an automobile battery
(b) $0.86 \mathrm{g}$ of $\mathrm{NaCl}$ in $1.00 \times 10^{2} \mathrm{g}$ of water $-$ a solution of sodium chloride for intravenous injection
(c) 46.85 g of codeine, $\mathrm{C}_{18} \mathrm{H}_{21} \mathrm{NO}_{3}$, in 125.5 $\mathrm{g}$ of ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$
(d) 25 g of I $_{2}$ in 125 g of ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$

Rikhil Makwana

Numerade Educator

Problem 39

Calculate the molality of each of the following solutions:
(a) $0.710 \mathrm{kg}$ of sodium carbonate (washing soda), $\mathrm{Na}_{2} \mathrm{CO}_{3}$, in $10.0 \mathrm{kg}$ of water $-$ a saturated solution at $0^{\circ} \mathrm{C}$
(b) $125 \mathrm{g}$ of $\mathrm{NH}_{4} \mathrm{NO}_{3}$ in $275 \mathrm{g}$ of water $-$ a mixture used to make an instant ice pack
(d) $0.372 \mathrm{g}$ of tetrahydropyridine, $\mathrm{C}_{5} \mathrm{H}_{9} \mathrm{N},$ in $125 \mathrm{g}$ of chloroform, $\mathrm{CHCl}_{3}$

Bhumika Jayee

Numerade Educator

Problem 40

The concentration of glucose, $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6},$ in normal spinal fluid is V $$\frac{75 \mathrm{mg}}{100 \mathrm{g}}$$. What is the molality of the solution?

Bhumika Jayee

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Problem 41

A 13.0\% solution of $\mathrm{K}_{2} \mathrm{CO}_{3}$ by mass has a density of $1.09 \mathrm{g} / \mathrm{cm}^{3}$. Calculate the molality of the solution.

Aadit Sharma

Numerade Educator

Problem 42

Why does 1 mol of sodium chloride depress the freezing point of 1 kg of water almost twice as much as 1 mol
of glycerin?

Rikhil Makwana

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Problem 43

Assuming ideal solution behavior, what is the boiling point of a solution of $115.0 \mathrm{g}$ of nonvolatile sucrose, $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11},$ in $350.0 \mathrm{g}$ of water?
(a) Outline the steps necessary to answer the question
(b) Answer the question

Bhumika Jayee

Numerade Educator

Problem 44

Assuming ideal solution behavior, what is the boiling point of a solution of $9.04 \mathrm{g}$ of $\mathrm{I}_{2}$ in $75.5 \mathrm{g}$ of benzene, assuming the $I_{2}$ is nonvolatile?
(a) Outline the steps necessary to answer the question.
(b) Answer the question.

Bhumika Jayee

Numerade Educator

Problem 45

Assuming ideal solution behavior, what is the freezing temperature of a solution of $115.0 \mathrm{g}$ of sucrose, $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11},$ in $350.0 \mathrm{g}$ of water?
(a) Outline the steps necessary to answer the question.
(b) Answer the question.

Bhumika Jayee

Numerade Educator

Problem 46

Assuming ideal solution behavior, what is the freezing point of a solution of $9.04 \mathrm{g}$ of $\mathrm{I}_{2}$ in $75.5 \mathrm{g}$ of benzene?
(a) Outline the steps necessary to answer the following question.
(b) Answer the question.

Bhumika Jayee

Numerade Educator

Problem 47

Assuming ideal solution behavior, what is the osmotic pressure of an aqueous solution of $1.64 \mathrm{g}$ of $\mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}$ in water at $25^{\circ} \mathrm{C}$ ? The volume of the solution is $275 \mathrm{mL}$.
(a) Outline the steps necessary to answer the question.
(b) Answer the question.

Bhumika Jayee

Numerade Educator

Problem 48

Assuming ideal solution behavior, what is osmotic pressure of a solution of bovine insulin (molar mass, $5700 \mathrm{g}$ mol $^{-1}$ ) at $18^{\circ} \mathrm{C}$ if $100.0 \mathrm{mL}$ of the solution contains $0.103 \mathrm{g}$ of the insulin?
(a) Outline the steps necessary to answer the question.
(b) Answer the question.

Bhumika Jayee

Numerade Educator

Problem 49

Assuming ideal solution behavior, what is the molar mass of a solution of $5.00 \mathrm{g}$ of a compound in $25.00 \mathrm{g}$ of carbon tetrachloride (bp $76.8^{\circ} \mathrm{C} ; K_{\mathrm{b}}=5.02^{\circ} \mathrm{C} / m$ ) that boils at $81.5^{\circ} \mathrm{C}$ at 1 atm?
(a) Outline the steps necessary to answer the question.
(b) Solve the problem.

Bhumika Jayee

Numerade Educator

Problem 50

A sample of an organic compound (a nonelectrolyte) weighing 1.35 g lowered the freezing point of $10.0 \mathrm{g}$ of benzene by $3.66^{\circ} \mathrm{C} .$ Assuming ideal solution behavior, calculate the molar mass of the compound.

Bhumika Jayee

Numerade Educator

Problem 51

A $1.0 \mathrm{m}$ solution of $\mathrm{HCl}$ in benzene has a freezing point of $0.4^{\circ} \mathrm{C}$. Is $\mathrm{HCl}$ an electrolyte in benzene? Explain.

David Collins

Numerade Educator

Problem 52

A solution contains $5.00 \mathrm{g}$ of urea, $\mathrm{CO}\left(\mathrm{NH}_{2}\right)_{2},$ a nonvolatile compound, dissolved in $0.100 \mathrm{kg}$ of water. If the vapor pressure of pure water at $25^{\circ} \mathrm{C}$ is 23.7 torr, what is the vapor pressure of the solution (assuming ideal solution behavior)?

Bhumika Jayee

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Problem 53

A 12.0-g sample of a nonelectrolyte is dissolved in 80.0 g of water. The solution freezes at -1.94 ^ C. Assuming ideal solution behavior, calculate the molar mass of the substance.

Bhumika Jayee

Numerade Educator

Problem 54

Arrange the following solutions in order by their decreasing freezing points: $0.1 \mathrm{m} \mathrm{Na}_{3} \mathrm{PO}_{4}, 0.1 \mathrm{m} \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$ $0.01 m \mathrm{CO}_{2}, 0.15 \mathrm{m} \mathrm{NaCl},$ and $0.2 \mathrm{m} \mathrm{CaCl}_{2}$

Bhumika Jayee

Numerade Educator

Problem 55

Calculate the boiling point elevation of $0.100 \mathrm{kg}$ of water containing $0.010 \mathrm{mol}$ of $\mathrm{NaCl}, 0.020$ mol of $$\mathrm{Na}_{2} \mathrm{SO}_{4}$$ and 0.030 mol of $\mathrm{MgCl}_{2}$, assuming complete dissociation of these electrolytes and ideal solution behavior.

Bhumika Jayee

Numerade Educator

Problem 56

How could you prepare a 3.08 $m$ aqueous solution of glycerin, $\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}_{3}$ ? Assuming ideal solution behavior, what is the freezing point of this solution?

Bhumika Jayee

Numerade Educator

Problem 57

A sample of sulfur weighing 0.210 g was dissolved in 17.8 g of carbon disulfide, $\mathrm{CS}_{2}\left(\mathrm{K}_{\mathrm{b}}=2.43^{\circ} \mathrm{C} / \mathrm{m}\right)$. If the boiling point elevation was $0.107^{\circ} \mathrm{C},$ what is the formula of a sulfur molecule in carbon disulfide (assuming ideal solution behavior)?

Bhumika Jayee

Numerade Educator

Problem 58

In a significant experiment performed many years ago, 5.6977 g of cadmium iodide in 44.69 g of water raised the boiling point $0.181^{\circ} \mathrm{C}$. What does this suggest about the nature of a solution of $\mathrm{CdI}_{2}$ ?

Rikhil Makwana

Numerade Educator

Problem 59

Lysozyme is an enzyme that cleaves cell walls. A 0.100-L sample of a solution of lysozyme that contains $0.0750 \mathrm{g}$ of the enzyme exhibits an osmotic pressure of $1.32 \times 10^{-3}$ atm at $25^{\circ} \mathrm{C}$. Assuming ideal solution behavior, what is the molar mass of lysozyme?

Bhumika Jayee

Numerade Educator

Problem 60

The osmotic pressure of a solution containing $7.0 \mathrm{g}$ of insulin per liter is 23 torr at $25^{\circ} \mathrm{C}$. Assuming ideal solution behavior, what is the molar mass of insulin?

Bhumika Jayee

Numerade Educator

Problem 61

The osmotic pressure of human blood is 7.6 atm at $37^{\circ} \mathrm{C}$. What mass of glucose, $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}$, is required to make 1.00 L of aqueous solution for intravenous feeding if the solution must have the same osmotic pressure as blood at body temperature, $37^{\circ} \mathrm{C}$ (assuming ideal solution behavior)?

Bhumika Jayee

Numerade Educator

Problem 62

Assuming ideal solution behavior, what is the freezing point of a solution of dibromobenzene, $\mathrm{C}_{6} \mathrm{H}_{4} \mathrm{Br}_{2},$ in $0.250 \mathrm{kg}$ of benzene, if the solution boils at $83.5^{\circ} \mathrm{C} ?$

Bhumika Jayee

Numerade Educator

Problem 63

Assuming ideal solution behavior, what is the boiling point of a solution of $\mathrm{NaCl}$ in water if the solution freezes at $-0.93^{\circ} \mathrm{C} ?$

Bhumika Jayee

Numerade Educator

Problem 64

The sugar fructose contains 40.0% C, 6.7% H, and 53.3% O by mass. A solution of 11.7 g of fructose in 325 g of ethanol has a boiling point of $78.59^{\circ} \mathrm{C}$. The boiling point of ethanol is $78.35^{\circ} \mathrm{C},$ and $K_{\mathrm{b}}$ for ethanol is $1.20^{\circ} \mathrm{C} / \mathrm{m}$. Assuming ideal solution behavior, what is the molecular formula of fructose?

Bhumika Jayee

Numerade Educator

Problem 65

The vapor pressure of methanol, $\mathrm{CH}_{3} \mathrm{OH}$, is 94 torr at $20^{\circ} \mathrm{C}$. The vapor pressure of ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}$, is 44 torr at the same temperature.
(a) Calculate the mole fraction of methanol and of ethanol in a solution of $50.0 \mathrm{g}$ of methanol and $50.0 \mathrm{g}$ of ethanol.
(b) Ethanol and methanol form a solution that behaves like an ideal solution. Calculate the vapor pressure of methanol and of ethanol above the solution at $20^{\circ} \mathrm{C}$.
(c) Calculate the mole fraction of methanol and of ethanol in the vapor above the solution.

Bhumika Jayee

Numerade Educator

Problem 66

The triple point of air-free water is defined as 273.16 K. Why is it important that the water be free of air?

Rikhil Makwana

Numerade Educator

Problem 67

Meat can be classified as fresh (not frozen) even though it is stored at $-1^{\circ} \mathrm{C}$. Why wouldn't meat freeze at this temperature?

Aadit Sharma

Numerade Educator

Problem 68

An organic compound has a composition of $93.46 \%$ C and $6.54 \%$ H by mass. A solution of 0.090 g of this compound in $1.10 \mathrm{g}$ of camphor melts at $158.4^{\circ} \mathrm{C}$. The melting point of pure camphor is $178.4^{\circ} \mathrm{C} . \mathrm{K}_{\mathrm{f}}$ for camphor is $37.7^{\circ} \mathrm{C} / \mathrm{m} .$ Assuming ideal solution behavior, what is the molecular formula of the solute? Show your calculations.

Bhumika Jayee

Numerade Educator

Problem 69

A sample of HgCl_ weighing 9.41 g is dissolved in 32.75 g of ethanol, C $_{2} \mathrm{H}_{5} \mathrm{OH}$ ( $K_{\mathrm{b}}=1.20^{\circ} \mathrm{C} / \mathrm{m}$ ). The boiling point elevation of the solution is $1.27^{\circ} \mathrm{C} .$ Is $\mathrm{HgCl}_{2}$ an electrolyte in ethanol? Show your calculations.

Bhumika Jayee

Numerade Educator

Problem 70

A salt is known to be an alkali metal fluoride. A quick approximate determination of freezing point indicates that $4 \mathrm{g}$ of the salt dissolved in $100 \mathrm{g}$ of water produces a solution that freezes at about $-1.4^{\circ} \mathrm{C}$. Assuming ideal solution behavior, what is the formula of the salt? Show your calculations.

Bhumika Jayee

Numerade Educator

Problem 71

Identify the dispersed phase and the dispersion medium in each of the following colloidal systems: starch dispersion, smoke, fog, pearl, whipped cream, floating soap, jelly, milk, and ruby.

Aadit Sharma

Numerade Educator

Problem 72

Distinguish between dispersion methods and condensation methods for preparing colloidal systems.

Rikhil Makwana

Numerade Educator

Problem 73

How do colloids differ from solutions with regard to dispersed particle size and homogeneity?

Aadit Sharma

Numerade Educator

Problem 74

Explain the cleansing action of soap.

Rikhil Makwana

Numerade Educator

Problem 75

How can it be demonstrated that colloidal particles are electrically charged?

Aadit Sharma

Numerade Educator