Kaplan MCAT General Chemistry Review

3. Under which of the following classifications of “acid” does H₂SO₄ fall?

I. Arrhenius

II. Brønsted-Lowry

III. Lewis

A. I only

B. II only

C. II and III only

D. I, II, and III

4. Suppose a few drops of acid rain fell on an open cut in the student’s hand. Would the bicarbonate (HCO₃^-) that exists in blood have any effect?

A. Yes, bicarbonate will buffer by accepting a H⁺ ion.

B. Yes, bicarbonate will buffer by donating a H⁺ ion.

C. No, bicarbonate does not act as a buffer.

D. There is not enough information in the passage to determine the correct answer.

5. If the rainwater that mixed with the pure water had original concentrations of [H₂SO₄] = 2 × 10^-3 M, [HNO₃] = 3.2 × 10^-3 M, what is the approximate final pH of the glass of water?

A. 1.2

B. 2.8

C. 3.4

D. 4.6

6. Which of the following is an INCORRECT pair of an acid and its conjugate base?

A. H₂SO₄ : HSO₄^-

B. CH₃COOH : CH₃COO^-

C. H₃O⁺ : H₂O

D. H₂CO₃ : CO₂

7. With which of the following statements would the student most likely NOT agree?

A. Acid rain has increased in frequency and intensity over the past 150 years.

B. Radicals play an integral role in the development of acid rain.

C. Acid rain lessens the conductive capabilities of water.

D. Acid rain is dangerous to the environment even though rain is naturally acidic.

QUESTIONS 8–9 ARE BASED ON THE FOLLOWING TITRATION CURVE:

8. What is the approximate ratio of pK_a1:pK_a2 for H₂CO₃?

A. 9.0:13.0

B. 7.8:12.0

C. 6.3:10.3

D. 6.0:11.1

9. What is the approximate ratio of equivalence points for H₂CO₃?

A. 9.0:13.0

B. 7.8:12.0

C. 6.3:10.3

D. 6.0:11.1

PASSAGE II (QUESTIONS 10–17)

The specific heat of a substance, c, measures the amount of heat required to raise the temperature of the mass of substance by a specific number of degrees. In certain cases, the chemical literature reports specific heat in terms of moles. Specific heat differs from heat capacity, a measurement of the amount of heat required to change the temperature of an object by a specific number of degrees.

In SI units, specific heat indicates the number of joules of heat needed to raise the temperature of 1 gram of the substance by 1 Kelvin. The specific heat of water reported in the chemical literature is 4.184 Jg^-1K^-1. Specific heat can be measured by a calorimeter, a device that insulates a sample from atmospheric conditions in order to measure the change in the sample material’s temperature over a set interval.

A student used a coffee cup calorimeter to compare the specific heat of water to the specific heat of a commercial fruit punch. The punch is made from a mixture of sugar water and powder flavoring. The student’s coffee cup calorimeter used a stack of two foam coffee cups and a thermometer, which the student stuck through a hole in a plastic lid covering the top cup in the stack. Such calorimeters are inexpensive and accurate experimental substitutes for industrial bomb calorimeters, which hold samples at constant volume to measure water temperature changes under high-pressure conditions.

To calibrate the calorimeter, the student combined known quantities of hot and cold water in the coffee cup until the thermometer read a steady temperature, as described in Table 1.

Hot Water Cold Water Volume 100 mL100 mLStart Temp 90°C20°CEnd Temp 54°C54°C

Table 1

Table 2 summarizes the specific heat data the student collected for the water and the fruit punch using the calibrated coffee cup setup.

Table 2

10. Which of the following values reports the molar specific heat of water from the chemical literature?

A. 4.184 Jmol^-1K^-1

B. 75.31 Jmol^-1K^-1

C. 4184 Jmol^-1K^-1

D. 75310 Jmol^-1K^-1

11. What measurement is also an intrinsic property of fruit punch?

A. Mass

B. Heat

C. Enthalpy

D. Viscosity

12. What is the heat capacity of the student’s coffee cup calorimeter?

A. 4.184 J/°C

B. 24.6 J/°C

C. 861 J/°C

D. 0.0246 J/°C

13. Suppose the student breaks his glass alcohol thermometer in the lab. The lab instructor’s only available replacement is a mercury thermometer. How would this change to the experimental setup affect the student’s measurements?

A. The calorimeter would measure a higher specific heat.

B. The calorimeter would measure a lower specific heat.

C. The thermometer would give a less precise specific heat measurement.

D. There would be no change to the specific heat measurement.

14. Which of the following rationales BEST explains why the student calibrated the coffee cup calorimeter before the experiment?

A. The coffee cup calorimeter can absorb heat.

B. The coffee cup calorimeter does not dry between uses.

C. The coffee cup calorimeter’s thermometer does not produce precise values.

D. The coffee cup calorimeter contents do not always reach equilibrium.