AP Chemistry: Multiple Choice Strategies

AP Chemistry: Multiple Choice Strategies

Although you might not like multiple-choice questions, there’s no denying the fact that guessing is easier on a multiple-choice question than it is on an essay question or a problem set. On a multiple-choice problem, the answer is always there in front of you; the trick is to find it amongst the forest of incorrect answers. Contrast this with Section II of the AP Chemistry exam. On that section, if you don’t know how to work a problem, you have to write down what you know and hope that the mythical King of Partial Credit is feeling kindly toward you that day.

We’ll talk more about Section II later. For now, let’s talk about what you’ll encounter on the AP Chemistry exam before you even see the first question.

 

Helpful Information In An Unhelpful Format

Imagine that your parents are forcing you to invite someone to a party that you are hosting. You don’t actually like this person, but your parents are insistent, so you have no choice but to comply. You give the acquaintance directions to the party, but you intentionally make the directions vague and difficult to use, filled with bland phrases like “Turn left at the light and then turn right a couple of miles down from there.” Your hope is that you’ve provided the required information but done so in a manner that will not help much.

This isn’t very nice of you, but it does provide a useful example. Before each section of the AP Chemistry exam, you will be given some information that you can use throughout the section. This information is presented just like those directions in the story above. It’s useful, but it doesn’t go out of its way to be easy to use. The periodic table presented before Section I is a stripped-down version that consists primarily of letters, numbers, and blocks. Any additional information that might be found on a regular periodic table is NOT there.

Now, if you’re familiar with the periodic table, you probably don’t need any of that extra information anyway. In other words, if you know enough about the periodic table to understand the periodic table at the front of the test, then you probably won’t need that periodic table very often.

So, in the end, the facts given at the front of the section are a bit of a wash. Still, keep in mind that they are there. There might be a question or two that require you to grab some specific information—such as the atomic number—from the periodic table, in which case having the table there is very handy. Most likely, though, there won’t be any overt indication that you need to use the table. In other words, the question won’t state, “Use the periodic table to help you on this problem,” or anything remotely like that.

Now that the introductory material has been covered, let’s talk about the 60 multiple-choice questions in Section I that you have 90 minutes to tackle.

The Stand-Alone Questions

These questions make up the bulk of the AP Chemistry exam. Each Stand-Alone question covers a specific topic, and then the next Stand-Alone hits a different topic. Each stem provides you with the information you need to answer the problem. Here’s a typical Stand-Alone:

If 100 mL of a 1 M HCl solution and 100 mL of a 5 M NaCl solution are mixed, what is the final molarity of the chloride (Clion)?

A. 1 M

B. 2 M

C. 3 M

D. 4 M

You get some information to start with, and then you’re expected to answer the question. The number of the question, 46, makes no difference since there’s no order of difficulty on the AP Chemistry exam. Tough questions are scattered between easy and medium questions with no pattern or reason.

Your ability to answer the Stand-Alones is going to make the greatest impact on your Section I score. This question type deserves some attention, yet it’s easier to talk about what isn’t in the Stand-Alone questions than what is there. Consider the following points:

  • There’s no order of difficulty. In other words, the problems don’t start out easy and gradually become tougher.
  • There’s no system to explain the order in which chemistry concepts appear in the section.
    The Stand-Alones look like a bunch of disconnected chemistry questions that appear one after the other. That’s just what they are. Since randomness rules the day, there’s no sense in answering these questions in consecutive order. A two-pass system should be used. Moreover, you can tweak the general idea of the two-pass system and apply it specifically to the AP Chemistry exam.

          

The Two-Pass System

If you wanted, you could take all the AP Chemistry questions and place them in a spectrum ranging from “fastest to answer” to “hardest or longest to answer.”

Those are the obvious ways to pace oneself, and many students do no more than that. But the more advanced your pacing system is, the more time you might have at the end of Section I to answer questions. To refine your two-pass abilities, consider the following three points when scanning through Section I:

Small Question Stems.

In test-speak, the portion of a problem that comes before the answer choices is typically called the question stem. Stem length varies on the AP Chemistry exam from eight-word simple sentences to elaborate 50-word descriptions of hypothetical situations. Either way, while you’re reading the question stem, time is ticking away. The longer the stem, the more time it takes you to read it. If you’re a fast reader, this might not be very much time. If you read at a more methodical rate, you might try first passing over the wordier problems.

Topics You Like.

Draw up two lists using the Big Ideas. Label one list “Concepts I Enjoy and Know About in Chemistry” and label the other list “Concepts That Are Not My Strong Points.” When you get ready to tackle the Stand-Alone section, keep these two lists in mind. On your first pass through the section, answer all the questions that deal with concepts you like and about which you are knowledgeable. When you come to a question that is on a subject that’s not one of your strong points, skip it and come back to it later. The overarching goal is to use your available time to answer as many questions correctly as possible.

Balanced Equations.

Balanced equations show up on the AP Chemistry exam in a number of places and in a variety of forms. Because these questions are easily recognizable, you might want to take a moment to zip through Section I and work all the equation questions in one go. (Of course, if balancing equations is one of those “Concepts That Are Not My Strong Points,” then this approach is not recommended.) Once these questions are finished, you can take off your Balancing Equation Hat and move on.

You don’t have much time to ponder every tough question, so trusting your instincts can keep you from getting bogged down and wasting time on a problem. You might not get every educated guess correct, but again, the goal isn’t to get a perfect score. The goal is to get a good score and to survive hard questions by going with your gut feelings.

Expert Tip

You have a little more than a minute per multiple-choice question. You won’t always need it, but sometimes you’ll need more. If you find yourself heading toward a minute, decide whether you’re making progress and will finish or whether you should go on and come back to that question.

On other problems, though, you might have no inkling of what the correct answer should be. In that case, turn to the following key idea.

Think Good Science

The AP Chemistry exam rewards good chemists. The test wants to foster future chemists by covering fundamental topics and sound laboratory procedure. What the test doesn’t want is bad science. It doesn’t want answers that are factually incorrect, too extreme to be true, or irrelevant to the topic at hand.

Yet these bad science answers invariably appear because it’s a multiple-choice test and you have to have four incorrect answer choices around the one right answer. So if you don’t know how to answer a problem, look at the answer choices and think “Good Science.” This may lead you to find some poor answer choices that can be eliminated.

If 100 mL of a 1 M HCl solution and 100 mL of a 5 M NaCl solution are mixed, what is the final molarity of the chloride (Clion)?

A. 0.5 M

B. 2 M

C. 4 M

D. 5 M

 

This is a Stand-Alone problem, but even if you don’t know how to answer this problem, you can use Good Science to give yourself a chance at guessing the right answer. Look at choice (D), 5 M. This value is used within the question stem. Because it appears in the stem, it’s unlikely to be the right answer. Why? There are two reasons:

  1. Even if you were from another planet, you could see that the “5” symbol in the question stem and in the answer choice are the same. Picking it for that reason doesn’t take any mental skills at all, and this AP exam is about testing your knowledge.
  2. Choice (D), 5 M, could be the answer if the problem was a trick question of some kind. But the AP Chemistry exam doesn’t generally use trick questions, so (D) is not the correct answer.

So eliminate (D). You could also use some Good Science and say, “If I’m adding 1 M to 5 M, the answer will probably be somewhere between these two values.” That gets rid of choice (A), 0.5 M. You now have a one-in-three shot of answering the problem. If you don’t know how to tackle this problem, these odds are pretty good.