MCQ Chapter 11 AP Chemistry

A 360. mg sample of aspirin, C9H8O4, (molar mass 180. g), is dissolved in enough water to produce 200. mL of solution. What is the molarity of aspirin in a 50. mL sample of this solution?

0.0100 M

A solution of methanol, CH3OH, in water is prepared by mixing together 128 g of methanol and 108 g of water. The mole fraction of methanol in the solution is closest to

0.40

A flask contains 0.25 mole of SO2(g), 0.50 mole of CH4(g), and 0.50 mole of O2(g). The total pressure of the gases in the flask is 800 mm Hg. What is the partial pressure of the SO2(g) in the flask?

160 mm Hg

A sealed vessel contains 0.200 mol of oxygen gas, 0.100 mol of nitrogen gas, and 0.200 mol of argon gas. The total pressure of the gas mixture is 5.00 atm. The partial pressure of the argon is

2.00 atm

Directions: Each set of lettered choices below refers to the numbered statements immediately following it. Select the one lettered choice that best fits each statement. A choice may be used once, more than once, or not at all in each set. Solid ethyl alcohol, C2H5OH A

A molecular solid with hydrogen bonding

The table above shows the structural formulas and molar masses for three different compounds. Which of the following is a list of the compounds in order of increasing boiling points?

Butane < acetone < 1-propano

In which of the following liquids do the intermolecular forces include dipole-dipole forces?

CH2F2(l)

Based on the information in the table above, which liquid, CS2(l) or CCl4(l), has the higher equilibrium vapor pressure at 25°C, and why?

CS2(l), because it has weaker London dispersion forces

The diagram above shows a thin-layer chromatogram of a mixture of products from a chemical reaction. The separation was performed using 50%50% ethyl acetate in hexane as the solvent (mobile phase) and silica gel as the polar stationary phase. On the basis of the chromatogram and the information about solvents in the table above, which of the following would be the best way to decrease the distance that the products travel up the plate?

Decrease the percentage of ethyl acetate in the solvent.

The London (dispersion) forces are weakest for which of the following gases under the same conditions of temperature and pressure?

H2

The liquefied hydrogen halides have the normal boiling points given above. The relatively high boiling point of HF can be correctly explained by which of the following? HF = +19 HCl = -85 HBr = -67 HI = -35

HF molecules tend to form hydrogen bonds.

Based on the results of the paper chromatography experiment shown above, which of the following can be concluded about the dye?

It has a weaker attraction for the stationary phase that it has for the mobile phase.

Substance & Normal boiling point HF = 293K F2 = 85K The electron cloud of HFHF is smaller than that of F2F2 , however, HFHF has a much higher boiling point than F2F2 has. Which of the following explains how the dispersion-force model of intermolecular attraction does not account for the unusually high boiling point of HFHF?

Liquid F2 has weak dispersion force attractions between its molecules, whereas liquid HF has both weak dispersion force attractions and hydrogen bonding interactions between its molecules.

Which statement best helps to explain the observation that NH3(l)NH3(�) boils at −28°C−28°C, whereas PH3(l)PH3(�) boils at −126°C−126°C?

NH3NH3 has hydrogen bonding that is stronger than the dipole-dipole forces in PH3PH3.

Steel is an alloy consisting of Fe with a small amount of C. Elemental Cr can be added to steel to make the steel less likely to rust; Cr atoms react with oxygen in the air to form a nonreactive layer of chromium oxide on the surface of the steel, preventing the oxidation of underlying Fe atoms. A sample of steel-chromium alloy contains 15 percent Cr by mass. Which of the following diagrams best shows a particle-level view of a surface section and an interior section of the alloy represented below at the left? (The atomic radii of the atoms involved are given in the table below at the right.)

Pick B or the one with nonreactive layer of chromium oxide on the surface of the steel Cr2O3

Based on the information in the table above, which of the compounds has the highest boiling point, and why?

Propanoic acid, because it can form intermolecular hydrogen bonds

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?

The particle is positively charged, because the oxygen atoms in water are attracted to it.

Four different liquid compounds in flasks at 20°C20°C are represented above. The table below identifies the compounds. Flask C shows the most particles in the vapor phase. Which of the following is not shown in the model but best helps to explain why flask C must contain pentane?

The strength of the intermolecular forces between the particles in the liquids

The structural formulas for two isomers of 1,2-dichloroethene1,2-dichloroethene are shown above. Which of the two liquids has the higher equilibrium vapor pressure at 20°C20°C, and why?

The trans-isomer, because it has only London dispersion forces, whereas the cis-isomer also has dipole-dipole interactions

Solid carbon tetrachloride, CCl4(s)CCl4(�), is represented by the diagram above. The attractions between the CCl4CCl4 molecules that hold the molecules together in the solid state are best identified as

intermolecular attractions resulting from temporary dipoles

The figure above shows two closed containers. Each contains the same volume of acetone in equilibrium with its vapor at the same temperature. The vapor pressure of the acetone is

the same in both containers because the temperature is the same