Deck 13: The Properties of Mixtures Solutions and Colloids

Question 1

Based only on the relative lattice energies of the compounds below, which one would be expected to have the lowest solubility in water?

A) NaBr
B) CaS
C) NaOH
D) KI
E) CsCl

Answer 1

CaS

Question 2

If a solute dissolves in an endothermic process

A) H bonds must exist between solvent and solute.
B) strong ion-dipole forces must exist in the solution.
C) the solute must be a gas.
D) the entropy of the solution is immaterial.
E) the entropy of the solution must be greater than that of its pure components.

Answer 2

the entropy of the solution must be greater than that of its pure components.

Question 3

Select the type of interaction that best describes the attraction between Mg²⁺ ions and water molecules.

A) dipole-dipole
B) dipole-induced dipole
C) ion-dipole
D) ion-induced dipole
E) ion-hydrogen bond

Answer 3

ion-dipole

Question 4

Potassium fluoride is used for frosting glass. Calculate the molarity of a solution prepared by dissolving 78.6 g of KF in enough water to produce 225 mL of solution.

A) 0.304 M
B) 0.349 M
C) 1.35 M
D) 3.29 M
E) 6.01 M

Question 5

Which of the following sets of conditions could exist when two liquids which are completely miscible in one another are mixed?

A) ΔH_soln > 0, entropy of system decreases
B) ΔH_soln ≈ 0, entropy of system decreases
C) ΔH_soln ≈ 0, entropy change of system ≈ 0
D) ΔH_soln ≈ 0, entropy of system increases
E) None of these choices are correct.

Question 6

The shape of a protein molecule is determined completely by

A) hydrogen bonding.
B) ion-dipole attractions.
C) dispersion forces.
D) disulfide bridges.
E) the sequence of amino acids in the chain.

Question 7

Which of the following pairs of ions is arranged so that the ion with the smaller charge density is listed first?

A) K⁺, Rb⁺
B) Cl^-, K⁺
C) Cl^-, Br^-
D) Ca²⁺, Ba²⁺
E) None of these choices are correct.

Question 8

The most abundant molecules in the cell membranes of most species are

A) proteins.
B) sugars.
C) phospholipids.
D) fatty acids.
E) steroids.

Question 9

When two pure substances are mixed to form a solution

A) heat is released.
B) heat is absorbed.
C) there is an increase in entropy.
D) there is a decrease in entropy.
E) entropy is conserved.

Question 10

Which of the following pairs of ions is arranged so that the ion with the larger (i.e., more negative) heat of hydration is listed first?

A) Br^-, K⁺
B) Mg²⁺, Sr ²⁺
C) Ca²⁺, Sc³⁺
D) Na⁺, Li⁺
E) None of these choices are correct.

Question 11

Which, if any, of the following features is common to soaps, detergents, phospholipids, and channel-forming antibiotics?

A) They all contain fatty acids.
B) They all contain phosphate groups.
C) They all contain polypeptide chains.
D) Their function depends on the dual polarity of their molecules.
E) None of these choices are correct.

Question 12

Under physiological conditions, amino acids in solution carry

A) no electrical charges.
B) a net positive charge, due to an -NH₃⁺ group or groups.
C) a net negative charge, due to a -COO^- group or groups.
D) both -NH₂ and -COOH groups.
E) both -NH₃⁺ and -COO^- groups.

Question 13

A solution of sucrose (sugar) in water is in equilibrium with solid sucrose. If more solid sucrose is now added, with stirring,

A) the concentration of the solution will increase.
B) the concentration of the solution will decrease.
C) the concentration of the solution will remain the same.
D) the volume of solution will increase.
E) a supersaturated solution will be produced.

Question 14

The Henry's Law constant (k) for carbon monoxide in water at 25°C is 9.71 × 10^-4 mol/(L·atm). How many grams of CO will dissolve in 1.00 L of water if the partial pressure of CO is 2.75 atm?

A) 3.53 × 10^-4 g
B) 2.67 × 10^-3 g
C) 9.89 × 10^-3 g
D) 7.48 × 10^-2 g
E) None of these choices are correct.

Question 15

Methane has a Henry's Law constant (k) of 9.88 × 10^-2 mol/(L·atm) when dissolved in benzene at 25°C. How many grams of CH₄ will dissolve in 3.00 L of benzene if the partial pressure of CH₄ is 1.48 atm?

A) 0.0667 g
B) 0.146 g
C) 2.34 g
D) 4.83 g
E) 7.02 g

Question 16

A saturated solution of carbon dioxide in water contains 3.00 g of CO₂ when the CO₂ partial pressure is 8.0 atm. What mass of CO₂ will escape if the partial pressure is lowered to 3.2 atm?

A) 0.90 g
B) 1.20 g
C) 1.40 g
D) 1.80 g
E) 2.20 g

Question 17

Soda drinks bubble when the bottle is opened because

A) the temperature of the soda increases.
B) exposure to atmospheric pressure squeezes the carbon dioxide from solution.
C) the partial pressure of carbon dioxide above the solution is reduced.
D) atmospheric nitrogen molecules displace carbon dioxide molecules.
E) the Henry's law constant changes due to the change in pressure.

Question 18

Consider the expression below, showing the terms which contribute to the heat of solution, ΔH_soln: ΔH_soln = ΔH_solute + ΔH_solvent + ΔH_mix
Which of the following sets correctly shows the signs (positive or negative) of the three terms on the right hand side of the equation?

A) ΔH_solute > 0; ΔH_solvent > 0; ΔH_mix > 0
B) ΔH_solute < 0; ΔH_solvent < 0; ΔH_mix < 0
C) ΔH_solute > 0; ΔH_solvent > 0; ΔH_mix < 0
D) ΔH_solute < 0; ΔH_solvent < 0; ΔH_mix > 0
E) ΔH_solute < 0; ΔH_solvent > 0; ΔH_mix < 0

Question 19

For a given solution, which of the following concentration values will change as temperature changes?

A) mass percent
B) molality
C) mole fraction
D) molarity
E) None of these choices are correct.

Question 20

Which of the following ions will be expected to have the most negative heat of hydration, ΔH_hydr?

A) Na⁺
B) Cs⁺
C) Ca²⁺
D) F^-
E) I^-

Question 21

The mole fraction of potassium nitrate in an aqueous solution is 0.0194. The solution's density is 1.0627 g/mL. Calculate the molarity of the solution.

A) 0.0194 M
B) 0.981 M
C) 1.05 M
D) 1.96 M
E) 19.4 M

Question 22

Copper(II) bromide is used as a wood preservative. What mass of CuBr₂ is needed to prepare 750.0 mL of a 1.25 M solution?

A) 134 g
B) 209 g
C) 372 g
D) 938 g
E) > 1 kg

Question 23

A 0.89% (w/v) sodium chloride solution is referred to as physiological saline solution because it has the same concentration of salts as human blood. What is the molarity of a physiological saline solution?

A) 0.0028 M
B) 0.015 M
C) 0.15 M
D) 0.30 M
E) 0.35 M

Question 24

Which of the following statements describes the correct method of preparation of 1.00 L of a 2.0 M urea solution? _urea = 60.06 g/mol

A) Dissolve 120 g of urea in 1.00 kg of distilled water.
B) Dissolve 120 g of urea in 880 g of distilled water.
C) Dissolve 120 g of urea in enough distilled water to produce 1.00 L of solution.
D) Dissolve 120 g of urea in 1.00 liter of distilled water.
E) The density of urea is needed in order to do this calculation.

Question 25

Potassium hydrogen phosphate is used in the preparation of nondairy powdered creamers. Calculate the molarity of a solution prepared by dissolving 238 g of K₂HPO₄ in enough water to produce 275 mL of solution.

A) 0.732 M
B) 0.865 M
C) 2.66 M
D) 4.97 M
E) None of these choices are correct.

Question 26

Calcium nitrite is used as a corrosion inhibitor in lubricants. What is the molality of a solution prepared by dissolving 18.5 g of calcium nitrite in 83.5 g of distilled water?

A) 0.0342 m
B) 0.0855 m
C) 0.222 m
D) 0.444 m
E) 1.68 m

Question 27

Cadmium bromide is used in photography and lithography. Calculate the molality of a solution prepared by dissolving 45.38 g of CdBr₂ in 375.0 g of water.

A) 0.03035 m
B) 0.01600 m
C) 0.1210 m
D) 0.4446 m
E) None of these choices are correct.

Question 28

What is the molality of a solution prepared by dissolving 86.9 g of diethyl ether, C₄H₁₀O, in 425 g of benzene, C₆H₆?

A) 0.362 m
B) 0.498 m
C) 2.01 m
D) 2.76 m
E) None of these choices are correct.

Question 29

Sodium hydroxide is a common ingredient in drain cleaners such as Drano. The mole fraction of sodium hydroxide in a saturated aqueous solution is 0.310. What is the molality of the solution?

A) 0.310 m
B) 0.690 m
C) 1.24 m
D) 12.4 m
E) 25.0 m

Question 30

A solution of ethanol (C₂H₆O) in water is sometimes used as a disinfectant. 1.00 L of this solution contains 553 g of ethanol and 335 g of water. What is the mole fraction of ethanol in this solution?

A) 0.377
B) 0.392
C) 0.553
D) 0.608
E) 0.623

Question 31

A solution of ethanol (C₂H₆O) in water is sometimes used as a disinfectant. 1.00 L of this solution contains 553 g of ethanol and 335 g of water. What is the molality of the ethanol in this solution?

A) 0.392 m
B) 0.608 m
C) 13.5 m
D) 33.6 m
E) 35.8 m

Question 32

The solubility of the oxidizing agent potassium permanganate is 7.1 g per 100.0 g of water at 25°C. What is the mole fraction of potassium permanganate in this solution?

A) 0.0080
B) 0.0086
C) 0.066
D) 0.45
E) 0.48

Question 33

Isoamyl salicylate ( = 208.25 g/mol) has a pleasant aroma and is used in perfumes and soaps. Which of the following combinations gives a 0.75 m solution of isoamyl salicylate in ethyl alcohol (d = 0.7893 g/mL)?

A) 117.2 g isoamyl salicylate in 950.0 mL of ethyl alcohol
B) 117.2 g isoamyl salicylate in 750.0 mL of ethyl alcohol
C) 117.2 g isoamyl salicylate in 750.0 mL of solution
D) 117.2 g isoamyl salicylate in 592.0 g of ethyl alcohol
E) None of these choices are correct.

Question 34

What volume of concentrated (14.7 M) phosphoric acid is needed to prepare 25.0 L of 3.0 M H₃PO₄?

A) 0.20 L
B) 0.57 L
C) 1.8 L
D) 3.6 L
E) 5.1 L

Question 35

Calculate the molarity of a solution prepared by diluting 1.85 L of 6.5 M KOH to 11.0 L.

A) 0.28 M
B) 0.91 M
C) 1.1 M
D) 3.1 M
E) 3.9 M

Question 36

What is the mole fraction of Ne in a mixture containing 10.1 g of Ne, 79.9 g of Ar, and 83.8 g of Kr?

A) 0.40
B) 0.25
C) 0.20
D) 0.14
E) 0.058

Question 37

Aqueous ammonia is commercially available in a solution that is 28% (w/w) ammonia. What is the mole fraction of ammonia in such a solution?

A) 0.017
B) 0.023
C) 0.012
D) 0.24
E) 0.29

Question 38

A 2.0% (w/v) solution of sodium hydrogen citrate, Na₂C₆H₆O₇, which also contains 2.5% (w/v) of dextrose, C₆H₁₂O₆, is used as an anticoagulant for blood which is to be used for transfusions. What is the molarity of the sodium hydrogen citrate in the solution?

A) 0.085 M
B) 0.19 M
C) 0.53 M
D) 1.2 M
E) 1.3 M

Question 39

Saccharin, one of the first non-nutritive sweeteners used in soft-drinks, is 500 times sweeter than sugar in dilute aqueous solutions. The solubility of saccharin is 1.00 gram per 290 mL of solution. What is the molarity of a saturated saccharin solution? ( saccharin = 183.2 g/mol)

A) 0.0188 M
B) 0.632 M
C) 1.58 M
D) 3.45 M
E) None of these choices are correct.

Question 40

The chemist, Anna Lytic, must prepare 1.00 kg of 15.0% (w/w) acetic acid using a stock solution which is 36.0% (w/w) acetic acid (d = 1.045 g/mL). Which of the following combinations will give her the solution she wants?

A) 417 mL of 36% acetic acid in 583 mL of distilled water
B) 417 g of 36% acetic acid in 583 g of distilled water
C) 360 mL of 36% acetic acid in 640 mL of distilled water
D) 360 g of 36% acetic acid in 640 g of distilled water
E) 150 g of 36% acetic acid in 850 g of distilled water

Question 41

Colligative properties depend on

A) the chemical properties of the solute.
B) the chemical properties of the solvent.
C) the masses of the individual ions.
D) the molar mass of the solute.
E) the number of particles dissolved.

Question 42

Which of the following aqueous solutions will have the lowest osmotic pressure?

A) 0.10 m KOH
B) 0.10 m RbCl
C) 0.05 m CaSO₄
D) 0.05 m BaCl₂
E) 0.10 m K₂SO₄

Question 43

The concentration of iodine in sea water is 60. parts per billion by mass. If one assumes that the iodine exists in the form of iodide anions, what is the molarity of iodide in sea water? (The density of sea water is 1.025 g/mL.)

A) 4.8 × 10^-13 M
B) 4.8 × 10^-10 M
C) 4.8 × 10^-7 M
D) 4.7 × 10^-4 M
E) 4.7 × 10^-1 M

Question 44

What concentration of aqueous FeCl₃ would have the same osmotic pressure as a 0.20 M solution of CaCl₂ at the same temperature, assuming ideal behavior?

A) 0.60 M
B) 0.40 M
C) 0.30 M
D) 0.15 M
E) 0.10 M

Question 45

Two aqueous solutions are prepared: 2.0 m Cu(NO₃)₂ and 2.0 m NaBr. Which of the following statements is true?

A) The Cu(NO₃)₂ solution has a higher vapor pressure and lower freezing point than the NaBr solution.
B) The Cu(NO₃)₂ solution has a higher vapor pressure and higher freezing point than the NaBr solution.
C) The Cu(NO₃)₂ solution has a lower vapor pressure and lower freezing point than the NaBr solution.
D) The Cu(NO₃)₂ solution has a lower vapor pressure and higher freezing point than the NaBr solution.
E) None of these choices are correct.

Question 46

Which of the following aqueous solutions should demonstrate the most non-ideal behavior?

A) 0.1 M NaI
B) 0.2 M CuSO₄
C) 0.5 M KBr
D) 2.0 M CuCl₂
E) 2.0 M CsCl

Question 47

Select the weakest electrolyte from the following set.

A) Na₂ SO₄
B) KCl
C) CH₃ CH₂ COOH, propionic acid
D) CaCl₂
E) LiOH

Question 48

Procaine hydrochloride ( = 272.77 g/mol) is used as a local anesthetic. Calculate the molarity of a 4.666 m solution which has a density of 1.1066 g/mL.

A) 2.272 M
B) 4.056 M
C) 4.216 M
D) 4.666 M
E) None of these choices are correct.

Question 49

How many moles of sulfate ions are present in 1.0 L of 0.5 M Li₂SO₄?

A) 0.5 mol
B) 1.0 mol
C) 1.5 mol
D) 2.0 mol
E) 3.0 mol

Question 50

From the following list of aqueous solutions and water, select the one with the highest boiling point.

A) 1.0 m KNO₃
B) 0.75 m NaCl
C) 0.75 m CuCl₂
D) 2.0 m C₁₂H₂₂O₁₁ (sucrose)
E) pure water

Question 51

Raoult's Law relates the vapor pressure of the solvent above the solution to its mole fraction in the solution. Which of the following is an accurate statement?

A) Raoult's Law applies exactly to all solutions.
B) Raoult's Law works best when applied to concentrated solutions.
C) Raoult's Law works best when applied to dilute solutions.
D) Raoult's Law applies only to non-ideal solutions.
E) None of these choices are correct.

Question 52

Select the strongest electrolyte from the following set.

A) CH₃CH₂OH, ethanol
B) LiNO₃
C) C₆H₁₂O₆, glucose
D) CC_l4
E) HF

Question 53

How many moles of solute particles are present in 100.0 mL of 2.50 M (NH₄)₃PO₄?

A) 0.100 mol
B) 0.250 mol
C) 0.500 mol
D) 0.750 mol
E) 1.00 mol

Question 54

The vapor pressure of pure acetone (propanone) is 266 torr. When a non-volatile solute is added, the vapor pressure of acetone above the solution falls to 232 torr. What is the mole fraction of acetone in the solution?

A) 0.87
B) 0.69
C) 0.32
D) 0.13
E) 0.045

Question 55

The vapor pressure of pure acetone (propanone) is 266 torr. When a non-volatile solute is added, the vapor pressure of acetone above the solution falls to 232 torr. What is the mole fraction of the non-volatile solute in the solution?

A) 0.87
B) 0.69
C) 0.32
D) 0.13
E) 0.045

Question 56

How many moles of bromide ions are present in 750.0 mL of 1.35 M MgBr₂?

A) 0.506 mol
B) 1.01 mol
C) 2.03 mol
D) 3.04 mol
E) None of these choices are correct.

Question 57

Which of the following aqueous solutions should demonstrate the most ideal behavior?

A) 0.1 M K₂SO₄
B) 0.1 M CaCl₂
C) 3.0 M LiF
D) 0.1 M MgSO₄
E) 0.1 M NaCl

Question 58

From the following list of aqueous solutions and water, select the one with the lowest freezing point.

A) 0.75 m (NH₄)₃PO₄
B) 1.0 m CaSO₄
C) 1.0 m LiClO₄
D) 1.5 m CH₃OH, methyl alcohol
E) pure water

Question 59

Children under the age of 6 with more than 0.10 ppm of lead in their blood can suffer a reduction in I.Q. or have behavior problems. What is the molality of a solution which contains 0.10 ppm of lead?

A) 4.8 × 10^-10 m
B) 4.8 × 10^-7 m
C) 4.8 × 10^-4 m
D) 4.8 × 10^-1 m
E) None of these choices are correct.

Question 60

Two aqueous are prepared: 1.00 m Na₂CO₃ and 1.00 m LiCl. Which of the following statements is true?

A) The Na₂CO₃ solution has a higher osmotic pressure and higher vapor pressure than the LiCl solution.
B) The Na₂CO₃ solution has a higher osmotic pressure and higher boiling point than the LiCl solution.
C) The Na₂CO₃ solution has a lower osmotic pressure and lower vapor pressure than the LiCI solution.
D) The Na₂CO₃ solution has a lower osmotic pressure and higher boiling point than the LiCl solution.
E) None of these choices are correct.

Question 61

Barbiturates are synthetic drugs used as sedatives and hypnotics. Barbital ( = 184.2 g/mol) is one of the simplest of these drugs. What is the boiling point of a solution prepared by dissolving 42.5 g of barbital in 825 g of acetic acid? K_b = 3.07°C/m; boiling point of pure acetic acid = 117.9°C

A) 117.0°C
B) 117.7°C
C) 118.1°C
D) 118.8°C
E) >120°C

Question 62

Cinnamaldehyde ( = 132.15 g/mol) is used as a flavoring agent. What mass of cinnamaldehyde must be added to 175 g of ethanol to give a solution whose boiling point is 82.7°C? K_b = 1.22°C/m, boiling point of pure ethanol = 78.5°C

A) 62.4 g
B) 67.8 g
C) 76.2 g
D) 78.5 g
E) 79.6 g

Question 63

Human blood has a molar concentration of solutes of 0.30 M. What is the osmotic pressure of blood at 25°C?

A) 0.012 atm
B) 0.62 atm
C) 6.8 atm
D) 7.3 atm
E) >10. atm

Question 64

Calculate the freezing point of a solution made by dissolving 3.50 g of potassium chloride ( = 74.55 g/mol) in 100.0 g of water. Assume ideal behavior for the solution; K_f = 1.86°C/m.

A) -1.7°C
B) -0.9°C
C) 0.0°C
D) 0.9°C
E) 1.7°C

Question 65

Hexachlorophene is used as a disinfectant in germicidal soaps. What mass of hexachlorophene ( = 406.9 g/mol) must be added to 125 g of chloroform to give a solution with a boiling point of 62.60°C? K_b = 3.63°C/m, boiling point of pure chloroform = 61.70°C

A) 12.6 g
B) 17.2 g
C) 31.0 g
D) 34.4 g
E) 101 g

Question 66

A 0.100 m K₂SO₄ solution has a freezing point of -0.43°C. What is the van't Hoff factor for this solution? K_f = 1.86°C/m

A) 0.77
B) 1.0
C) 2.3
D) 3.0
E) >3.0

Question 67

Which one of the following pairs of dispersed phases and dispersing media can never form a colloid?

A) solid and gas
B) liquid and gas
C) solid and solid
D) liquid and liquid
E) gas and gas

Question 68

Benzaldehyde ( = 106.1 g/mol), also known as oil of almonds, is used in the manufacture of dyes and perfumes and in flavorings. What would be the freezing point of a solution prepared by dissolving 75.00 g of benzaldehyde in 850.0 g of ethanol? K_f = 1.99°C/m, freezing point of pure ethanol = -117.3°C.

A) -117.5°C
B) -118.7°C
C) -119.0°C
D) -120.6°C
E) < -121°C

Question 69

Lysine is an amino acid that is an essential part of nutrition but which is not synthesized by the human body. What is the molar mass of lysine if 750.0 mL of a solution containing 8.60 g of lysine has an osmotic pressure of 1.918 atm? Temperature = 25.0°C

A) 110. g/mol
B) 146 g/mol
C) 220. g/mol
D) 1340 g/mol
E) 1780 g/mol

Question 70

The Tyndall effect

A) is observed in concentrated solutions.
B) is observed only in dilute solutions.
C) is observed in colloidal dispersions.
D) is caused by Brownian motion.
E) is used to determine the osmotic pressure of solutions.

Question 71

An emulsion is a dispersion consisting of a

A) solid in a liquid.
B) liquid in a liquid.
C) gas in a liquid.
D) liquid in a solid.
E) gas in a solid.

Question 72

Safrole is used as a topical antiseptic. Calculate the vapor pressure of a solution prepared by dissolving 0.75 mol of safrole in 950 g of ethanol ( = 46.07 g/mol). P°_ethanol = 50.0 torr at 25°C.

A) 1.8 torr
B) 11 torr
C) 15 torr
D) 40 torr
E) 48 torr

Question 73

Determine the freezing point of a solution that contains 0.31 mol of sucrose in 175 g of water. K_f = 1.86°C/m

A) 3.3°C
B) 1.1°C
C) 0.0°C
D) -1.1°C
E) -3.3°C

Question 74

Calculate the vapor pressure of a solution prepared by dissolving 0.500 mol of a non-volatile solute in 275 g of hexane ( = 86.18 g/mol) at 49.6°C. P°_hexane = 400.0 torr at 49.6°C.

A) 54 torr
B) 154 torr
C) 246 torr
D) 346 torr
E) 400. torr

Question 75

All solutions are mixtures.

Question 76

Which of the following aqueous liquids will have the lowest freezing point?

A) 0.5 m C₁₂H₂₂O₁₁ (sucrose)
B) 0.5 m Ca(NO₃)₂
C) 0.5 m NiSO₄
D) 0.5 m Li₃PO₄
E) pure water

Question 77

A 0.100 m MgSO4 solution has a freezing point of -0.23°C. What is the van't Hoff factor for this solution? K_f = 1.86°C/m

A) 0.62
B) 1.0
C) 1.2
D) 2.0
E) 4.0

Question 78

Carbon tetrachloride, once widely used in fire extinguishers and as a dry cleaning fluid, has been found to cause liver damage to those exposed to its vapors over long periods of time. What is the boiling point of a solution prepared by dissolving 375 g of sulfur (S8, = 256.5 g/mol) in 1250 g of CCl₄? Kb = 5.05°C/m, boiling point of pure CCl₄ = 76.7°C?

A) 70.8°C
B) 75.2°C
C) 78.2°C
D) 82.6°C
E) >85°C

Question 79

Diethyl ether has a vapor pressure of 400.0 torr at 18°C. When a sample of benzoic acid is dissolved in ether, the vapor pressure of the solution is 342 torr. What is the mole fraction of benzoic acid in the solution?

A) 0.0169
B) 0.0197
C) 0.145
D) 0.855
E) None of these choices are correct.

Question 80

Dimethylglyoxime, DMG, is an organic compound used to test for aqueous nickel(II) ions. A solution prepared by dissolving 65.0 g of DMG in 375 g of ethanol boils at 80.3°C. What is the molar mass of DMG? K_b = 1.22°C/m, boiling point of pure ethanol = 78.5°C

A) 44.1 g/mol
B) 65.8 g/mol
C) 117 g/mol
D) 131.6 g/mol
E) 553 g/mol