The following are actual questions taken from previously administered MCAT exams.
Read the passage carefully and choose the best answer to each question. The questions are to be answered on the basis of what is stated or implied in the passage.
But man is not destined to vanish. He can be killed, but he cannot be destroyed, because his soul is deathless and his spirit is irrepressible. Therefore, though the situation seems dark in the context of the confrontation between the superpowers, the silver lining is provided by the amazing phenomenon that the very nations which have spent incalculable resources and energy for the production of deadly weapons are desperately trying to find out how they might never be used. They threaten each other, intimidate each other, and go to the brink, but before the total hour arrives they withdraw from the brink.
1. The main point from the author's view is that
- Man's soul and spirit cannot be destroyed by superpowers.
- Man's destiny is not fully clear or visible.
- Man's soul and spirit are immortal.
- Man's safety is assured by the delicate balance of power in terms of nuclear weapons.
- Human society will survive despite the serious threat of total annihilation.
Answer : E
2. The phrase 'Go to the brink' in the passage means
- Retreating from extreme danger.
- Declare war on each other.
- Advancing to the stage of war but not engaging in it.
- Negotiate for peace.
- Commit suicide.
Answer : C
3. In the author's opinion
- Huge stockpiles of destructive weapons have so far saved mankind from a catastrophe.
- Superpowers have at last realized the need for abandoning the production of lethal weapons.
- Mankind is heading towards complete destruction.
- Nations in possession of huge stockpiles of lethal weapons are trying hard to avoid actual conflict.
- There is a silver lining over the production of deadly weapons.
Answer : D
4. 'Irrepressible' in the second line means
Answer : D
5. A suitable title for the above passage is
- Destruction of mankind is in evitable.
- Man's desire to survive inhibits use of deadly weapons.
- Mounting cost of modern weapons.
- Threats and intimidation between super powers.
- Cowardly retreat by man
Answer : B
Physical SciencesA series of chemical reactions was carried out to study the chemistry of lead.
Initially, 15.0 mL of 0.300 M Pb(NO3)2(aq) was mixed with 15.0 mL of 0.300 M Na2SO4(aq). All the Pb(NO3)2 reacted to form Compound A, a white precipitate. Compound A was removed by filtration.
Next, 15.0 mL of 0.300 M KI(aq) was added to Compound A. The mixture was agitated and some of Compound A dissolved. In addition, a yellow precipitate of PbI2(s) was formed.
The PbI2(s) was separated and mixed with 15.0 mL of 0.300 M Na2CO3(aq). A white precipitate of PbCO3(s) formed. All of the PbI2(s) was converted into PbCO3(s).
The PbCO3(s) was removed by filtration and a small sample gave off a gas when treated with dilute HCl.
Some sample questions on this passage are as follows:
1. Which of the following reactions depicts the formation of the gas in Reaction 4?
- PbCO3(s) + 2 HCl(aq) = PbCl2(aq) + CO2(g) + H2O(l)
- Na2CO3(aq) + 2 HCl(aq) = 2 NaCl(aq) + CO2(g) + H2O(l)
- PbCO3(s) + 2 HCl(aq) = PbC2(s) + Cl2(g) + H2O(l)
- PbI 2(s) + HCl(aq) = PbCl2(aq) + HI(g)
Explanation: Reaction 4 is shown in the following equation, which is answer choice A.
PbCO3(s) + 2 HCl(aq) = PbCl2(aq) + CO2(g) + H2O(l)
Answers B and D do not show a reaction involving PbCO3(s), as required by Reaction 4. Answer C shows an implausible and unbalanced equation. Thus, answer choice A is the best answer.
2. The identity of Compound A is:
Explanation: Reaction 1 is shown in the following equation.
Pb(NO3)2(aq) + Na2SO4(aq) = PbSO4(s) + 2 NaNO3(aq)
Compound A, the white solid, is PbSO4(s). Neither the reactant Pb(NO3)2 nor the product NaNO3 can precipitate because all nitrates and sodium salts are water soluble. PbI2 cannot precipitate because iodide is not present. Thus, answer choice D is the best answer.
3. Pb(OH)2(s) is slightly soluble in water. How would the amount of Pb(OH)2(s) that normally dissolves in 1 L of water be affected if the pH were 9.0?
- Less would dissolve.
- The same amount would dissolve.
- More would dissolve.
- There is no way to predict the effect of the change in pH of the water.
Explanation: The dissolution of Pb(OH)2(s) is represented by the following equation.
Pb(OH)2(s)=Pb2(aq) + 2 OH-(aq)
At pH 9, the concentration of OH-(aq) is greater than the concentration of OH-(aq) at pH 7. According to Le Châtelier's principle, the additional common ion, OH-(aq), will shift the position of equilibrium to the left, and less Pb(OH)2 will dissolve. Thus, answer choice A is the best answer.
4. A soluble form of Pb2+can be carefully added to a solution to sequentially precipitate and separate anions present in the solution. When Pb2+is added, in what order will the following anions be precipitated?
- SO42- then I-
- CO32- then I-
- SO42- then CO32-
- I- then CO32-
Explanation: The reactions described in the passage show that lead(II) is successively precipitated as PbSO4, PbI2, and PbCO3. This sequence shows (assuming equal anion concentrations, as must be done here) that PbCO3 is less soluble than PbI2, and PbI2 is less soluble than PbSO4. The order in which the anions precipitate Pb2- is: CO32- then I- then SO42-. When this sequence is applied to the question, answer choice B is in the correct order, and answers A, C, and D are all in the opposite order. Thus, answer choice B is the best answer.
5. How many moles of Na+ ions are there in the initial Na2SO4(aq) solution used in Reaction 1?
- 0.0018 mole
- 0.009 mole
- 0.045 mole
- 0.090 mole
Explanation: The initial Na2SO4(aq) solution in Reaction 1 is 15 mL of 0.300 MNa2SO4(aq).
(15.0 mL) ( 1 L ) (0.300 mol Na2SO4) (2 mol Na+)
(1000 mL) (1 L Na2SO4(aq) ) (1 mol Na2SO4)
= 0.00900 mol = Answer B
# Scientific inquiry is rooted in the desire to discover, but there is no discovery so important that in its pursuit a threat to human life can be tolerated.
Write a unified essay in which you perform the following tasks. Explain what you think the above statements means. Describe a specific situation in which a threat to human life might be tolerated in the pursuit of scientific discovery. Discuss what you think determines when the pursuit of scientific discovery is more important than the protection of human life.
# Politicians too often base their decisions on what will please the voters, not on what is best for the country.
Write a unified essay in which you perform the following tasks. Explain what you think the above statement means. Describe a specific situation in which a politician might make an unpopular decision for the good of the country. Discuss the principles you think should determine whether political decisions should be made to please the voters or to serve the nation.
# An understanding of the past is necessary for solving the problems of the present.
Write a unified essay in which you perform the following tasks. Explain what you think the above statement means. Describe a specific situation in which solving a current problem might not require an understanding of the past. Discuss what you think determines whether or not the past should be considered in solving the problems of the present.
# Wealthy politicians cannot offer fair representation to all the people.
Write a unified essay in which you perform the following tasks. Explain what you think the above statement means. Describe a specific situation in which a wealthy politician might offer fair representation to all people. Discuss what you think determines whether a wealthy politician can or cannot offer fair representation to all the people.
# In a free society, laws must be subject to change.
Write a unified essay in which you perform the following tasks. Explain what you think the above statement means. Describe a specific situation in which a law should not be subject to change in a free society. Discuss what you think determines whether or not a law in a free society should be subject to change.
by Hannah Roberts, staff writer