chem ch 3 exam

Based on the data in the tables above, which of the following statements provides the best prediction for the boiling point of NaCl ? A NaCl will have a lower boiling point than NaF because the coulombic attractions are weaker in NaCl than in NaF . B NaCl will have a boiling point between that of NaF and MgO because the covalent character of the bonds in NaCl is intermediate between that of MgO and NaF. C NaCl will have a higher boiling point than MgO because the ions are spaced farther apart in NaCl . D NaCl will have a higher boiling point than MgO because the energy required to transfer electrons from the anion to the cation is larger in NaCl than in MgO .

A

Under which of the following conditions of temperature and pressure would 1.0 mol of the real gas CO2(g) behave most like an ideal gas? A Temperature(K)Pressure(atm)1000.1 B Temperature(K)Pressure(atm)100100 C Temperature(K)Pressure(atm)8000.1 D Temperature(K)Pressure(atm)8001 E Temperature(K)Pressure(atm)800100

C

A 0.5 mol sample of He(g) and a 0.5 mol sample of Ne(g) are placed separately in two 10.0 L rigid containers at 25°C. Each container has a pinhole opening. Which of the gases, He(g) or Ne(g), will escape faster through the pinhole and why? A He(g) will escape faster because the He(g) atoms are moving at a higher average speed than the Ne(g) atoms. B Ne(g) will escape faster because its initial pressure in the container is higher. C Ne(g) will escape faster because the Ne(g) atoms have a higher average kinetic energy than the He(g) atoms. D Both gases will escape at the same rate because the atoms of both gases have the same average kinetic energy.

A

An ionic crystal is added to water and starts to dissolve as shown in the particulate representation above. Based on the orientation of the water molecules, what can be assumed about the charge of the hydrated particle indicated by the arrow? A The particle is positively charged, because the oxygen atoms in water are attracted to it. B The particle is negatively charged, because hydrogen atoms in water are attracted to it. C The particle is both positively and negatively charged, because the water molecules are attracted to it. D The particle is neutral, because the dipoles of the water molecules neutralize the charge of the particle.

A

M+ is an unknown metal cation with a +1 charge. A student dissolves the chloride of the unknown metal, MCl, in enough water to make 100.0 mL of solution. The student then mixes the solution with excess AgNO3 solution, causing AgCl to precipitate. The student collects the precipitate by filtration, dries it, and records the data shown below. (The molar mass of AgCl is 143 g/mol.) Mass of unknown chloride, MCl0.74 gMass of filter paper0.80 gMass of filter paper plus AgCl precipitate2.23 g Which of the following diagrams best represents the AgNO3 solution before the reaction occurs?

A

Which of the following behaves most like an ideal gas at the conditions indicated? A H2(g) molecules at 10-3 atm and 200oC B O2(g) molecules at 20 atm and 200oC C SO2(g) molecules at 20 atm and 200oC D NH3(g) molecules at 20 atm and 200oC E NH3(g) molecules at 20 atm and 300oC

A

Of the following, the best explanation for the fact that most gases are easily compressed is that the molecules in a gas A are in constant motion B are relatively far apart C have relatively small masses D have a real, nonzero volume E move slower as temperature decreases

B

Solution 0.1MHC2H3O2(aq) 0.1MKI(aq) 0.1MCH3OH(aq) Of the three solutions listed in the table above, which one, if any, has the greatest electrical conductivity and why? A. 0.1MHC2H3O2(aq) because its molecules have the most atoms. B. 0.1MKI(aq) because KI completely dissociates in water to produce ions. C. 0.1MCH3OH(aq) because its molecules can form hydrogen bonds. D. All three solutions have the same electrical conductivity because the concentrations are the same.

B

The diagram above represents the photoelectric effect for a metal. When the metal surface is exposed to light with increasing frequency and energy of photons, electrons first begin to be ejected from the metal when the energy of the photons is 3.3×10−19J3.3×10−19J. ColorWavelengthRed647−760nm647−760nmOrange585−647nm585−647nmYellow575−585nm575−585nmGreen491−575nm491−575nmBlue424−491nm424−491nmViolet300−424nm300−424nm Using the wavelength information provided above, what is the color of the light? A Red B Orange C Yellow D Blue

B

The molecular formula and molar mass of two straight-chain hydrocarbons are listed in the table above. Based on the information in the table, which compound has the higher boiling point, and why is that compound's boiling point higher? A C4H10 ,because it has more hydrogen atoms, resulting in more hydrogen bonding B C4H10 , because it has more electrons, resulting in greater polarizability and stronger dispersion forces C C2H6 , because its molecules are smaller and they can get closer to one another, resulting in stronger dispersion forces D C2H6 , because its molecules are more polar, resulting in stronger dipole-dipole attractions

B

When 6.0 L of He(g) and 10. L of N2(g), both at 0oC and 1.0 atm, are pumped into an evacuated 4.0 L rigid container, the final pressure in the container at 0oC is A 2.0 atm B 4.0 atm C 6.4 atm D 8.8 atm E 16 atm

B

Which of the following molecules is least soluble in water?

B - CCL4

A rigid metal tank contains oxygen gas. Which of the following applies to the gas in the tank when additional oxygen is added at constant temperature? A The volume of the gas increases. B The pressure of the gas decreases. C The average speed of the gas molecules remains the same. D The total number of gas molecules remains the same. E The average distance between the gas molecules increases.

C

PCl5(g) ⇄ PCl3(g) + Cl2(g) PCl5(g) decomposes into PCl3(g) and Cl2(g) according to the equation above. A pure sample of PCl5(g) is placed in a rigid, evacuated 1.00 L container. The initial pressure of the PCl5(g) is 1.00 atm. The temperature is held constant until the PCl5(g) reaches equilibrium with its decomposition products. The figures below show the initial and equilibrium conditions of the system. Which of the following is the most likely cause for the increase in pressure observed in the container as the reaction reaches equilibrium? A A decrease in the strength of intermolecular attractions among molecules in the flask B An increase in the strength of intermolecular attractions among molecules in the flask C An increase in the number of molecules, which increases the frequency of collisions with the walls of the container D An increase in the speed of the molecules that then collide with the walls of the container with greater force

C

A student prepared five solutions of CuSO4 with different concentrations, and then filled five cuvettes, each containing one of the solutions. The cuvettes were placed in a spectrophotometer set to the appropriate wavelength for maximum absorbance. The absorbance of each solution was measured and recorded. The student plotted absorbance versus concentration, as shown in the figure above. Which of the following is the most likely explanation for the variance of the data point for the 0.600 M CuSO4 solution? A The cuvette into which the 0.600 M solution was placed had some water droplets inside. B The cuvette into which the 0.600 M solution was placed was filled slightly more than the other cuvettes. C The wavelength setting was accidentally moved away from that of maximum absorbance. D The cuvette used for the 0.600 M solution had not been wiped clean before being put in the spectrophotometer.

D

Benzene, C6H6 , has the structure shown above. Considering the observation that benzene is only sparingly soluble in water, which of the following best describes the intermolecular forces of attraction between water and benzene? A Benzene is nonpolar, therefore there are no forces between water and benzene. B The H atoms in benzene form hydrogen bonds with the O atoms in water. C Benzene is hydrophobic, therefore there is a net repulsion between water and benzene. D There are dipole-induced dipole and London dispersion interactions between water and benzene.

D

In a paper chromatography experiment, a sample of a pigment is separated into two components, X and Y, as shown in the figure above. The surface of the paper is moderately polar. What can be concluded about X and Y based on the experimental results? A X has a larger molar mass than Y does. B Y has a larger molar mass than X does. C X is more polar than Y. D Y is more polar than X.

D

The average kinetic energy of the gas molecules is A greatest in container A B greatest in container B C greatest in container C D the same in all three containers

D

The diagram above represents the absorption spectrum for a pure molecular substance. Which of the following correctly indicates the type of transition observed for the substance in each of the regions of the absorption spectrum? A Region XRegion YRegion ZMolecular vibrationMolecular rotationElectronic transition B Region XRegion YRegion ZElectronic transitionMolecular rotationMolecular vibration C Region XRegion YRegion ZMolecular rotationMolecular vibrationElectronic transition D Region XRegion YRegion ZElectronic transitionMolecular vibrationMolecular rotation

D

A 0.20 mol sample of MgCl2(s) and a 0.10 mol sample of KCl(s) are dissolved in water and diluted to 500 mL. What is the concentration of Cl- in the solution? A 0.15 M B 0.30 M C 0.50 M D 0.60 M E 1.0 M

E