CH302 All HW

A semi-permeable membrane can withstand an osmotic pressure of 0.75 atm. What molarity of aqueous magnesium bromide solution would reach the limit for this membrane? (Assume RT = 25 L·atm·mol-1) a) 0.01 M b) 0.01 mM c) 0.03 mM d) 0.03 M

a) 0.01 M Magnesium bromide will dissociate into 3 particles.

A hypothetical compound MX3 has a molar solubility of 0.00562 M. What is the value of Ksp for MX3? a) 2.69 x 10^-8 b) 9.48 x 10^-5 c) 3.16 x 10^-5 d) 2.99 x 10^-9

a) 2.69 x 10^-8

What will be the freezing point of a solution of 8 moles of sodium dichromate (Na2Cr2O7) dissolved in 16 kg of water? Use the following values: Kb = 0.512 K/m Kf = 1.86 K/m a) 270.2 K b) 272.2 K c) 2.8°C d) 275.8 K

a) 270.2 K

Consider the following reaction: 2NH3 + CH3OH --> products How much NH3 is needed to react completely with 34g of CH3OH? a) 36g NH3 b) 128g NH3 c) 9g NH3 d) 1.3g NH3

a) 36g NH3

What is the net ionic equation for the reaction between aqueous solutions of Na3PO4 and CuSO4? a) 3Cu2+ + 2PO43- --> Cu3(PO4)2 b) 2Na+ + SO42- --> Na2SO4 c) Cu2+ + PO43- --> CuPO4 d) No reaction occurs since no precipitate is formed.

a) 3Cu2+ + 2PO43- --> Cu3(PO4)2 Both copper (II) sulfate and sodium phosphate are soluble. This is a metathesis reaction with the products copper (II) phosphate (Cu3(PO4)2) and sodium sulfate(Na2SO4). The sodium sulfate is soluble (and therefore contains all of the spectator ions), but the copper (II) phosphate is insoluble and will form a precipitate. To obtain the net ionic equation we cancel the spectator ions, leaving only the species that react.

The value of Ksp for SrSO4 is 2.8x10-7. What is the solubility of SrSO4 in moles per liter? a) 5.3 x 10^-4 b) 1.4 x 10^-7 c) 2.8 x 10^-7 d) 7.6 x 10^-7

a) 5.3 x 10^-4

Rank the following liquids by vapor pressure from lowest to highest: C5H12, CH4, C3H8, C2H6, C4H10. a) C5H12 < C4H10 < C3H8 < C2H6 < CH4 b) C2H6 < C3H8 < C4H10 < C5H12 < CH4 c) CH4 < C2H6 < C3H8 < C4H10 < C5H12 d) CH4 < C5H12 < C4H10 < C3H8 < C2H6

a) C5H12 < C4H10 < C3H8 < C2H6 < CH4 All of these molecules are non-polar so their strongest IMF is dispersion forces. To rank their IMFs, remember that larger molecules exhibit stronger dispersion forces. Also, remember that vapor pressure is inversely proportional to IMF. So, to rank vapor pressure from smallest to largest, we simply rank the molecules from greatest IMFs to smallest IMFs.

Which would have a higher vapor pressure: ethanol (C2H5OH) or dimethyl ether (CH3OCH3)? a) dimethyl ether b) They would have the same vapor pressure as their molecular weights are the same. c) ethanol d) It is impossible to tell unless the amount of each substance is known.

a) dimethyl ether Dimethyl ether will have the higher vapor pressure since it has smaller IMFs to hold it in the liquid phase. Both molecules are polar and have similar dispersion forces, but ethanol can perform hydrogen bonding.

The freezing point of seawater is about -1.85°C. If seawater is an aqueous solution of sodium chloride, calculate the molality of seawater. The kf for water is 1.86 K/m. a) 0.995 m b) 0.497 m c) 1.99 m d) -0.497 m

b) 0.497 m Remember that the normal freezing point for water is 0°C, so the freezing point of sea water depresses this by 1.85°C (or 1.85 K). The van't Hoff factor for NaCl is i = 2.

A hypothetical ionic substance T3U2 ionizes to form T2+ and U3- ions. The solubility of T3U2 is 4.04x10-20 mol/L. What is the value of the solubility-product constant? a) 1.08x10^-97 b) 1.16 x 10^-95 c) 1.63x10^-39 d) 9.79x10^-39

b) 1.16 x 10^-95

Catalase (a liver enzyme) dissolves in water. A 14mL solution containing 0.166g of catalase exhibits an osmotic pressure of 1.2 Torr at 20°C. What is the molar mass of catalase? a) 2.81x10^5 g/mol b) 1.81x10^5 g/mol c) 1.49x10^5 g/mol d) 1.69x10^5 g/mol

b) 1.81x10^5 g/mol

What is the change in entropy ( Svap ) for the vaporization of ethanol ( Hvap = 38.6 kJ·mol-1 ) at its standard boiling temperature (78.4°C)? a) 0.110 J·mol-1·K-1 b) 110 J·mol-1·K-1 c) 492 J·mol-1·K-1 d) 0.492 J·mol-1·K-1

b) 110 J·mol-1·K-1

Which of the following would change the vapor pressure of a sample of water in a closed container? 1. decreasing the size of the container 2. lower the container temperature 3. removing water from the container a) 2 and 3 b) 2 only c) 1, 2, and 3 d) 1 and 2

b) 2 only The size of a container and the amount of substance contained in it are irrelevant to vapor pressure. Temperature is a strong determinant vapor pressure.

Determine the molar solubility of some salt with the generic formula AB2 if Ksp = 2.56x102. a) 1 M b) 4 M c) 0.1 M d) 10 M

b) 4 M

A solution of AgI contains 1.9 M Ag+. Ksp of AgI is 8.3 x 10-17. What is the maximum I- concentration that can exist in this solution? a) 1.9 M b) 4.4x10^-17 M c) 8.3x10^-17 M d) 1.6x10^-16 M

b) 4.4x10^-17 M

How many moles of ions are contained in 1.27 L of a 1.75 M solution of Mg(NO3)2? a) 0.741 mol b) 6.67 mol c) 4.45 mol d) 2.22 mol

b) 6.67 mol

The ΔH°vap of methane is 8.519 kJ·mol-1 and its ΔS°vap is 85.58 J·mol-1·K-1. What is the boiling point of methane? a) 0.09954°C b) 99.54 K c) 372.54 K d) 0.09954 K

b) 99.54 K

Theoretically, it should be harder to dissolve ( NaCl / Al2S3 ) in water because the (higher / lower) the charge density of a substance, the lower its solubility. a) NaCl, lower b) Al2S3, higher c) Al2S3, lower d) NaCl, higher

b) Al2S3, higher Al2S3 has a higher charge density ( Al3+, S2- ) than NaCl (Na+, Cl-). High charge density corresponds to high lattice energy and thus much more endothermic dissolution (requiring more energy to dissolve, thus making it a less spontaneous process).

Rank the following salts from least to most molar solubility: BiI Ksp = 7.7x10-19 Cd3(AsO4)2 Ksp = 2.2x10-33 AlPO4 Ksp = 9.8x10-21 CaSO4 Ksp = 4.9x10-5 a)Cd3(AsO4)2 < BiI < AlPO4 < CaSO4 b) AlPO4 < BiI < Cd3(AsO4)2 < CaSO4 c) Cd3(AsO4)2 < AlPO4 < BiI < CaSO4 d) CaSO4 < BiI < AlPO4 < Cd3(AsO4)2

b) AlPO4 < BiI < Cd3(AsO4)2 < CaSO4 Molar solubility can be approximated by taking the nth root of the Ksp where n is the number of ions in the salt. Doing so results in approximate molar solubilities of 10-10, 10-7, 10-11, and 10-3 for bismuth iodide, cadmium arsenate, aluminum phosphate, and calcium sulfate respectively. Arranging these from least to greatest produces the correct answer.

The Ksp eqution for sodium bicarbonate (NaHCO3) should be written as: a) Ksp = [NaH2+][CO32-] b) Ksp = [Na+][H+][CO32-] c) Ksp = [Na+][H+][C4+][O2-]3 d) Ksp = [Na+][HCO3-]

b) Ksp = [Na+][H+][CO32-] Ksp is calculated using the concentrations of every ion the compound can break into. Sodium bicarbonate can obviously break into Na+ cations and HCO3- anions, but bicarbonate can further act as an acid, breaking into H+ cations and CO32- anions.

Some distilled water is added to an empty beaker. A gram of copper (II) nitrate is added to the beaker and while the water is being stirred. After a few minutes, what is in the beaker? a) solid copper, nitrate ions, and water b) copper ions, nitrate ions, and water c) nitrogen gas, copper atoms, electrons, and water d) solid copper (II), nitrate, and water

b) copper ions, nitrate ions, and water All nitrates are soluble in water, so the copper (II) nitrate dissolves. Soluble ionic compounds are strong electrolytes. So, the copper (II) nitrate also dissociates into its cation and anion part: Cu2+ and NO3-.

Which of the phase changes below might have a H = 11.6 kJ·mol-1? a) condensation b) evaporation c) deposition d) freezing

b) evaporation As dH is positive, the phase change must be an endothermic process (requiring the input of heat). Of the answer choices, only evaporation takes place when heat is added to the system. The others require the removal of heat.

For solutions of a non-electrolyte, the van't Hoff factor is: a) i = 3 b) i = 1 c) i = 2 d) i = 0

b) i = 1 Non-electrolytes do not dissociate. Therefore, one dissolved molecule will stay in ONE piece, and will have a van't Hoff factor of i = 1.

__________ are made when __________ are dissolved in __________. a) solutions, solvents, solutes b) solutions, solutes, solvents c) solvents, solutes, solutions d) solutes, solutions, solvents

b) solutions, solutes, solvents

Red blood cells contain Na+ ions, K+ ions, and water. If we place some red blood cells into a beaker full of pure water, what will happen to them? a) they will wiggle around rapidly b) they will swell and burst c) nothing d) they will shrivel and collapse

b) they will swell and burst This illustrates the process of osmosis. Water can move through the membrane of the blood cells in either direction, but because there is less water inside the cells than outside (there is more salt inside the cells), there will be a net flow of water into the cells. So, they will swell and possibly even burst.

Which of the following is a possible combination of values for Hlattice and Hhydration respectively for a salt whose dissolution is endothermic? a) -560, +560 b) +500, -520 c) +640, -620 d) -200, -304

c) +640, -620 dH{solution} = dH{lattice} + dH{hydration} For the dissolution to be endothermic, dH{solution} must be positive, so the two values must add to a positive number.

What is the vapor pressure of carbon disulfide at its normal boiling point? a) Not enough informaiton. b) 2.0 atm c) 1.0 atm d) 22.4 atm

c) 1.0 atm At ANY liquid's normal boiling point, the vapor pressure = 1.0 atm.

Which of the following would increase the solubility of a gas in water? 1. increase the temperature of the water 2. decrease the temperature of the water 3. increase the pressure of the gas above the water a) 2 only b) 1 only c) 2 and 3 d) 1 and 3

c) 2 and 3 The solubility of a gas increases as the temperature of the water decreases and the pressure of the gas increases.

What would be the molar solubility of Li3PO4 (Ksp = 2.37 x 10-4) in a 1M LiCl solution? a) 1.54 x 10^-2 b) 5.44 x 10^-2 c) 2.37 x 10^-4 d) 1.24 x 10^-1

c) 2.37 x 10^-4

An unknown liquid has a vapor pressure of 88 mmHg at 45°C and 39 mmHg at 25°C. What is its heat of vaporization? a) 2000 J/mol b) 32,000 kJ/mol c) 32 kJ/mol d) 2000 kJ/mol

c) 32 kJ/mol Clausius-Clapeyron equation

Two aqueous solutions are separated by a semi-permeable membrane: Solution A = 0.34 M KCl Solution B = 0.34 M MgCl2 Which of the following statements is TRUE? a) There is no net flow of H2O molecules from one solution to another. b) There is a net flow of Cl- ions from solution B to solution A. c) There is a net flow of H2O molecules from solution A to solution B. d) There is a net flow of H2O molecules from solution B to solution A.

c) There is a net flow of H2O molecules from solution A to solution B. Semipermeable membranes are only permeable to water (the solvent), so only H2O can pass through it. Even though both solutions have equal concentrations of solute, there are more IONS in solution B. Therefore, water will move from solution A to solution B to try and make the concentrations of the ions in both solutions equal.

At 20°C the vapor pressure of dry ice is 56.5 atm. If 10g of dry ice (solid CO2) is placed in an evacuated 0.25 L chamber at a constant 20°C, will all of the solid sublime? a) None of dry ice would sublime. b) There is not enough information to answer this quesiton. c) Yes. d) Some of the dry ice will sublime, but not all of it.

c) Yes. The dry ice will sublime until the pressure inside the chamber is equal to the vapor pressure. 10g of CO2 is 0.227 moles of CO2. Plugging this into the ideal gas law ( PV = nRT ) will find that if all the dry ice sublimes, the pressure will be less than the vapor pressure. So, the solid will never reach equilibrium with the gas and the system will turn entirely into gas.

Which of the following statements is ALWAYS true about deposition? a) None of the other answers are correct b) dS > 0 c) dH < 0 d) dG < 0

c) dH < 0

Ice is heated at a constant pressure until it melts and vaporizes. What signs are assoiated with the total change in entropy and enthalpy ( S and H ) for this sample of water? a) dS = - , dH = - b) dS = + , dH = - c) dS = + , dH = + d) dS = - , dH = +

c) dS = + , dH = +

Use the phase diagram for CO2 provided below to answer the following question: At 300K and 10 bar, what is the stable phase of carbon dioxide? https://utexas.instructure.com/courses/1185987/files/41204652/preview a) liquid carbon dioxide b) solid carbon dioxide c) gaseous carbon dioxide d) carbon dioxide as supercritical fluid

c) gaseous carbon dioxide The point on the phase diagram that represents the intersection of 300K and 10 bar lies squarely in the region labeled "gas." Thus, CO2 is most stable in the gaseous state under the provided conditions.

Both ammonia (NH3) and phosphine (PH3) are soluble in water. Which is least soluble and why? a) ammonia because it does not form hydrogen bonds with water molecules b) phosphine because the P-H bonds are so strong that they cannot break to enable phosphine to hydrogen-bond with water c) phosphine because it does not form hydrogen bonds with water molecules d) ammonia because the N-H bonds are so strong that they cannot break to enable the ammonia to hydrogen-bond with water

c) phosphine because it does not form hydrogen bonds with water molecules PH3 is less soluble because it cannot form hydrogen bonds with water. The P-H bond, while polar, is not strong enough to form hydrogen bonds. Hydrogen bonding requires either N-H, O-H, or F-H bonds.

CaSO4 has a Ksp = 3x10-5. In which of the following would CaSO4 be the most soluble? a) 1.0 M CaCl2(aq) b) 0.5 M K2SO4(aq) c) pure water d) CaSO4 would have the same solubility in all three of these solutions

c) pure water CaSO4 would have the same solubility in any solution that does not contain Ca2+ or SO42- ions. However, if a solution does contain one of these two ions, then the Q will reach and exceed Ksp faster than in a solution that does not contain these ions. That is, a precipitate of CaSO4 will form faster in a solution that contains either Ca2+ or SO42- ions. So, in this problem, CaSO4 would be most soluble in pure water as 0.5 M K2SO4(aq) contains SO42- ions and 1.0 M CaCl2(aq) contains Ca2+ ions.

In a closed vessel containing water, the pressure is 18 torr. If we add more water to the vessel, this equilibrium pressure would... a) change, but it is not possible to know if it will increase or decrease without more information. b) decrease. c) remain the same. d) increase.

c) remain the same. Vapor pressure is the pressure exerted by a vapor that exists in equilibrium with its liquid phase. As long as there is ANY liquid, the vapor pressure remains the same (the actual amount of liquid is irrelevant). The only thing that affects the vapor pressure of a substance is the temperature.

Rank the following aqueous solutions from lowest to highest boiling point: 0.5 m NaCl, 1 m KCl, 0.5 m BaCl2, and 1 m Ba(NO3)2. All salt are dissolved in water. a) 1 m Ba(NO3)2 < 0.5 m NaCl < 0.5 m BaCl2 < 1 m KCl b) 1 m KCl < 1 m Ba(NO3)2 < 0.5 m NaCl < 0.5 m BaCl2 c) 0.5 m BaCl2 < 1 m KCl < 1 m Ba(NO3)2 < 0.5 m NaCl d) 0.5 m NaCl < 0.5 m BaCl2 < 1 m KCl < 1 m Ba(NO3)2

d) 0.5 m NaCl < 0.5 m BaCl2 < 1 m KCl < 1 m Ba(NO3)2 All of the solutions are composed of strong electrolytes and thus their van't Hoff factors must be taken into account as well as their molalities: Aqueous Solution: van't Hoff x molality = boiling point increase factor 0.5 m NaCl: 2 x 0.5 = 1 0.5 m BaCl2: 3 x 0.5 = 1.5 1 m KCl: 2 x 1 = 2 1 m Ba(NO3)2: 3 x 1 = 3

Calculate the vapor pressure at 20°C of a solution containing 0.61g of naphthalene in 16g of chloroform (CHCl3). Naphthalene (C10H8) has a low vapor pressure and may be assumed to be nonvolatile. The vapor pressure of chloroform at 20°C is 156 torr. a) The vapor pressure would not change as naphthalene is considered non-volatile. b) 28.10 torr c) 20.90 torr d) 150.65 torr

d) 150.65 torr 0.61g of naphthalene = 0.00476 mols, 16g of chloroform = 0.134 mols

Use the phase diagram for CO2 in the question above to answer the following: A sample of carbon dioxide is stored at 10,000 bar and 250K. This sample is then decompressed to 1 bar at constant temperature. Then, at constant pressure it is heated to 400K. Next, it is compressed at constant temperature to 200 bar. According to the phase diagram, how many phase transitions has the sample of carbon dioxide gone through, and what is its final state? a) 3, liquid b) 2, gas c) 3, supercritical fluid d) 2, supercritical fluid

d) 2, supercritical fluid Navigate through each process using the phase diagram. In the first decompression, the solid is decompressed and becomes a liquid and then a gas (2 phase transitions). Upon heating and then compressing, it becomes a supercritical fluid (no phase transition).

How much heat is required to heat 2 grams of ice at -30°C to steam at 100°C. Use the approximate values below for your calculations: c{ice} = 2 J/g*C dH{fusion} = 340 J/g c{water} = 4 J/g*C dH{vap} = 2260 J/g c{steam} = 2 J/g*C a) 6.00 kJ b) 1.60 kJ c) 6120 kJ d) 6.12 kJ

d) 6.12 kJ

Determine if a precipitate will form when 0.96g Na2CO3 is combined with 0.2g BaBr2 in a 10L solution. (For BaCO3, Ksp = 2.8x10-9). a) BaCO3 does not precipitate b) BaBr2 will remain in solid form as it is insoluble in water. c) It is impossible to know if any BaCO3 will precipitate with the information given. d) BaCO3 precipitates

d) BaCO3 precipitates As 'Q' > Ksp, BaCO3 precipitates.

Rank the following in terms of decreasing miscibility in C8H18 (octane), a major component of gasoline: C2H5Cl (chloroethane), H2O (water), C2H5F (fluoroethane), and C9H20 (nonane). a) C2H5Cl > C2H5F > H2O > C9H20 b) H2O > C2H5F > C2H5Cl > C9H20 c) H2O > C9H20 > C2H5Cl > C2H5F d) C9H20 > C2H5Cl > C2H5F > H2O

d) C9H20 > C2H5Cl > C2H5F > H2O Octane is a non-polar solvent and thus ranking in terms of decreasing miscibility requires ranking in terms of decreasing non-polar character (from least polar to most polar).

What ions are present in solution after aqueous solutions of Cu(NO3)2 and K2S are mixed? Assume we mixed stoichiometric equivalent amounts of both reactants and 100% reaction. a) Cu2+, NO3-, K+, S2- b) Cu2+, S2- c) No ions are present as both products form precipitates. d) K+, NO3-

d) K+, NO3- Both copper (II) nitrate and potassium sulfide are soluble. This is a metathesis rection with the products copper (II) sulfide (CuS) and potassium nitrate (KNO3). KNO3 is soluble and will exist as K+ and NO3- ions in solution. CuS is insoluble and will form a precipitate.

Consider liquid ethane (CH3CH3) and liquid methanol (CH3OH). Which would you expect to have a larger H of vaporization? a) It is impossible to tell unless you know the amount of each liquid involved. b) Ethane, because it has stronger IMFs. c) Methanol because it has a larger molar mass. b) Methanol, because it has stronger IMFs.

d) Methanol, because it has stronger IMFs. How large the dH of vaporization is of a substance is related to the strength of the IMFs involved, not the substance's mass nor how much of it is present. Methanol can perform hydrogen bonding (the strongest form of IMF) while ethane molecules are only held together by dispersion forces (the weakest form of IMF). Therefore, as the IMFs in methanol are greater, you would expect it to have a bigger dH of vaporization.

Which of the following is primarily responsible for limiting the number of trophic levels in most ecosystems? a) 45.0 moles of H2 b) 33.8 moles of H2 c) 15.0 moles of H2 d) No matter how many moles of H2 are added, 30.0 moles of NH3 cannot be produced.

d) No matter how many moles of H2 are added, 30.0 moles of NH3 cannot be produced. 14.5 moles of N2 can only produce a maximum of 29.0 moles of NH3, regardless of how much H2 is added to the reaction. 14.5 moles N2 x (2 mol NH3/1 mol N2) = 29 mol NH3

Pure water is saturated with PbCl2. In this saturated solution, which of the following is true? a) Ksp = [Pb2+]2[Cl-] b) [Pb2+] = [Cl-] c) Ksp = [Pb2+][Cl-] d) [Pb2+] = 0.5[Cl-]

d) [Pb2+] = 0.5[Cl-] As PbCl2 will dissociate into one Pb2+ ion and two Cl- ions for every one molecule dissolved, the concentration of Pb2+ ions should be half that of Cl- ions. The Ksp = [Pb2+][Cl-]2.

In which of the following pairs do both compounds have a van't Hoff factor (i) of 2? a) glucose and sodium chloride b) perchloric acid and barium hydroxide c) sodium sulfate and potassium chloride d) sodium chloride and magnesium sulfate

d) sodium chloride and magnesium sulfate Both sodium chloride and magnesium sulfate are strong electrolytes that dissociate to form one cation and one anion, a total of 2 ions (or a van't Hoff factor of i = 2).

Molar solubility is... a) the total molarity of the solution. b) equal to the Ksp. c) the number of moles that dissolve to give one liter of super-saturated solution. d) the number of moles that dissolve to give one liter of saturated solution.

d) the number of moles that dissolve to give one liter of saturated solution. The molar solubility of a compound is the number of moles that dissolve to give one liter of saturated solution.

Consider two empty containers A and B whose volumes are 10mL and 20mL respectively. 1mL of liquid water is put into each container and the temperature of each container is adjusted to 20°C. The gas pressure in container B, which still has some liquid water in it, is found to be 17 torr. How would the pressure in container A and the amount of liquid water in container A compare to that of container B? a) the pressure would be the same, there would be an equal amount of liquid water b) the pressure would be greater, there would be an equal amount of liquid water c) the pressure would be greater, there would be less liquid water d) the pressure would be the same, there would be more liquid water

d) the pressure would be the same, there would be more liquid water As both containers are at the same temperature, the vapor pressure of water will be the same in each container. However, since container A is smaller than container B, it will take less gaseous water to reach this vapor pressure. Therefore, the two containers should have the same vapor pressure, though container A should more liquid water present than in the larger container B.