CH302 Exam One

Which of the following is a possible combination of values for Hlattice and Hhydration respectively for a salt whose dissolution is endothermic?

+640, -620

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)

0.01 M

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.

0.497 m

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.

0.5 m NaCl < 0.5 m BaCl2 < 1 m KCl < 1 m Ba(NO3)2

Ice floats on water. For most other substances, however, the solid sinks in the liquid. Classify each of these statements based on whether they describe water or most other substances. 1. In the phase diagram, the solid-liquid coexistence line has a negative slope. 2. Molecules are closest in the solid phase. 3. Molecules are closest in the liquid phase. 4. The solid is less dense than the liquid. 5. In the phase diagram, the solid-liquid coexistence line has a positive slope.

1. water 2. other 3. water 4. water 5. other

What is the vapor pressure of carbon disulfide at its normal boiling point?

1.0 atm

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?

1.16 x 10-95

At 1 atm, how much energy is required to heat 49.0 g of H2O(s) at −18.0 °C to H2O(g) at 123.0 °C? Heat transfer constants can be found in this table.

1.52 x 10^2

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?

1.81x105 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)?

110 J·mol-1·K-1

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.

150.65 torr

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

2 and 3

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

2 only

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?

2, supercritical fluid

What would be the molar solubility of Li3PO4 (Ksp = 2.37 x 10-4) in a 1M LiCl solution?

2.37 x 10-4

A hypothetical compound MX3 has a molar solubility of 0.00562 M. What is the value of Ksp for MX3?

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:

270.2 K

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?

32 kJ/mol

A certain substance has a heat of vaporization of 71.26 kJ/mol. At what Kelvin temperature will the vapor pressure be 3.00 times higher than it was at 341 K?

357 K

Consider the following reaction: 2NH3 + CH3OH products How much NH3 is needed to react completely with 34g of CH3OH?

36g NH3

What is the net ionic equation for the reaction between aqueous solutions of Na3PO4 and CuSO4?

3Cu2+ + 2PO43- \longrightarrow Cu3(PO4)2

Determine the molar solubility of some salt with the generic formula AB2 if Ksp = 2.56x102.

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?

4.4x10-17 M

The heat of vaporization of water is 40.66 kJ/mol. How much heat is absorbed when 2.04 g of water boils at atmospheric pressure?

4.60 kJ

How many grams of benzene, C6H6, can be melted with 57.2 kJ of heat energy? The molar heat of fusion of benzene is 9.95 kJ/mol.

449 g

A certain liquid has a vapor pressure of 92.0 Torr at 23.0 °C and 372.0 Torr at 45.0 °C. Calculate the value of ΔH∘vap for this liquid. Calculate the normal boiling point of this liquid.

49.2 kJ/mol 60.3 degrees celsius

Calculate the heat energy released when 25.0 g of liquid mercury at 25.00° C is converted to solid mercury at its melting point.

5.08 x 10^-1

The value of Ksp for SrSO4 is 2.8x10-7. What is the solubility of SrSO4 in moles per liter?

5.3 x 10-4

If you combine 250.0 mL of water at 25.00 °C and 140.0 mL of water at 95.00 °C, what is the final temperature of the mixture? Use 1.00 g/mL as the density of water.

50.13 degrees C

To treat a burn on your hand, you decide to place an ice cube on the burned skin. The mass of the ice cube is 12.5 g, and its initial temperature is −10.1 °C. The water resulting from the melted ice reaches the temperature of your skin, 30.8 °C. How much heat is absorbed by the ice cube and resulting water? Assume that all the water remains in your hand. Constants may be found in this table.

6.04 x 10^3

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 = 2J delta Hfus = 340 J c water = 4J delta H vap = 2260 J c steam = 2J

6.12 kJ

How many moles of ions are contained in 1.27 L of a 1.75 M solution of Mg(NO3)2?

6.67 mol

How many grams of ethanol, C2H5OH, can be boiled with 707.3 kJ of heat energy? The molar heat of vaporization of ethanol is 38.6 kJ/mol.

8.44 x 10^2 g

The specific heat of a certain type of cooking oil is 1.75 J/(g·°C). How much heat energy is needed to raise the temperature of 2.97 kg of this oil from 23 °C to 191 °C?

8.73 x 10^5 J

Two 20.0‑g ice cubes at −10.0 °C are placed into 245 g of water at 25.0 °C. Assuming no energy is transferred to or from the surroundings, calculate the final temperature of the water after all the ice melts. heat capacity of H2O(s) 37.7 J/(mol⋅K) heat capacity of H2O(l) 75.3 J/(mol⋅K) enthalpy of fusion of H2O 6.01 kJ/mol

9.59 degrees celsius

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?

99.54 K

Based on the data in this table Solid Triple point Normal melting point A 0.91 atm, 124 °C 108 °C B 0.35 atm, -17 °C 50 °C C 0.0072 atm, 88 °C 89 °C which solids will melt under applied pressure?

A

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.

Al2S3, higher

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

AlPO4 < BiI < Cd3(AsO4)2 < CaSO4

Which reactions have a positive ΔSrxn? a. A(s) + 2B(g) -> C(g) b. A(s) + B(g) -> 2C(g) c. A(g) + B(g) -> C(g) d. 2A(g) + B(g) -> 4C(g)

B, D

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).

BaCO3 precipitates

Rank the following liquids by vapor pressure from lowest to highest: C5H12, CH4, C3H8, C2H6, C4H10.

C5H12 < C4H10 < C3H8 < C2H6 < CH4

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). Correct Answer

C9H20 > C2H5Cl > C2H5F > H2O

Which two statements about propene and ethanol are true? Ethanol forms hydrogen bonds, whereas propene has dipole-dipole interactions. Propene has a higher boiling point than ethanol due to its double bond. Ethanol has a lower vapor pressure than propene at a given temperature. Both propene and ethanol have London forces and dipole-dipole forces. Of the two compounds, only ethanol forms hydrogen bonds.

Ethanol has a lower vapor pressure than propene at a given temperature. Of the two compounds, only ethanol forms hydrogen bonds.

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.

K+, NO3-

The Ksp eqution for sodium bicarbonate (NaHCO3) should be written as:

Ksp = [Na+][H+][CO32-]

Consider liquid ethane (CH3CH3) and liquid methanol (CH3OH). Which would you expect to have a larger H of vaporization?

Methanol, because it has stronger IMFs.

Given that you have 14.5 moles of N2, how many moles of H2 are theoretically needed to produce 30.0 moles of NH3 according to reaction below? N2 + 3H2 2NH3

No matter how many moles of H2 are added, 30.0 moles of NH3 cannot be produced.

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?

There is a net flow of H2O molecules from solution A to solution B.

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?

Yes

Pure water is saturated with PbCl2. In this saturated solution, which of the following is true?

[Pb2+] = 0.5[Cl-]

Which of the following statements is ALWAYS true about deposition?

\DeltaH < 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?

\DeltaS = + , \DeltaH = +

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?

copper ions, nitrate ions, and water

Which would have a higher vapor pressure: ethanol (C2H5OH) or dimethyl ether (CH3OCH3)?

dimethyl ether

The boiling point for ethane, CH3CH3, is −88.6 °C. The boiling point for ethanol, CH3CH2OH, is 78.3 °C. Which has the higher vapor pressure at a given temperature?

ethane

Which of the phase changes below might have a H = 11.6 kJ·mol-1?

evaporation

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?

gaseous carbon dioxide

Without referring to a data table, rank the compounds by standard molar entropy. CH3OH (g), N2 (g), O2 (g)

highest entropy: CH3OH (g) O2 lowest entropy: N2

Arrange these compounds by their expected vapor pressure. H2O, Br2, NCl3

highest: Br2, NCl3, lowest: H2O

For solutions of a non-electrolyte, the van't Hoff factor is:

i = 1

Both ammonia (NH3) and phosphine (PH3) are soluble in water. Which is least soluble and why? You Answered

phosphine because it does not form hydrogen bonds with water molecules

CaSO4 has a Ksp = 3x10-5. In which of the following would CaSO4 be the most soluble?

pure water

In a closed vessel containing water, the pressure is 18 torr. If we add more water to the vessel, this equilibrium pressure would...

remain the same.

In which of the following pairs do both compounds have a van't Hoff factor ( ) of 2?

sodium chloride and magnesium sulfate

__________ are made when __________ are dissolved in __________.

solutes, solutions, solvents

For liquids, which of the factors affect vapor pressure? temperature intermolecular forces volume surface area humidity

temperature, IMF

Molar solubility 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?

the pressure would be the same, there would be more liquid water

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?

they will swell and burst