The average score on the Advanced Placement Examination in Chemistry will be around 50 percent.
The selection of the questions and the length of the exam is done carefully.
You can use well-known concepts and methods to get the maximum score you deserve.
The multiple-choice section is designed to test your recall of fundamental chemical concepts and the use of these concepts to solve basic chemistry problems.
The questions are designed for various levels of difficulty and cover the entire syllabus.
Only one of the four choices is the most appropriate answer.
There is no penalty for leaving a question unanswered.
The free-response section is the most difficult part of the chemistry exam.
It requires a good knowledge of the theories, principles, concepts, and facts of chemistry, the same things that will earn a good score on the multiple-choice section.
This section demands readable presentations.
The first three questions are long, constructed-response questions that can include mathematical solutions to problems of 4 to 8 parts.
In words, explain your approach to the problem.
Good methods are used when doing the math.
If you don't skip steps, you will make fewer mistakes.
Explain any nonstandard symbols with complete equations with equal signs.
Determine if the result is reasonable or not.
If some work is shown, partial credit is given.
If a number from a previous part of the question is missing, make up a number and solve the problem by telling the reader what you are doing.
Correct methods will earn a large portion of the allotted score.
Four of the last five questions are constructed-response questions.
They often involve interpretation of a theory or application of a process such as writing Lewis structures.
Answers should be concise and correct.
There are technical errors that detract from the presentation.
To support statements of fact, you should include appropriate examples with sketches, structures, and graphs.
If you don't know the answer, take a guess.
There is no punishment for wrong answers.
Your odds of getting a correct answer are 1 out of 4 when you are running out of time.
If you have time, you should read the question and answer it to the best of your ability.
There are many clues in chemistry that allow you to judge your answers.
To read between the lines of a question and to do a quick evaluation of your answer, there are some hints below.
A distracter is a response that looks good at first glance but has a serious flaw that makes it incorrect.
More distracters will be found in each question if the design of the test is better.
One way to make a response incorrect is to use subtle changes in the wording.
As the temperature increases, chemicals become more smilng.
As the temperature increases, most chemicals become more stable.
The reaction is cold.
The reaction is cold.
It is important to read questions and understand terminology.
The differences between "most" and "all" in the first set and between "exothermic" and "endothermic" in the second are significant.
Before selecting an answer to a nonnumerical problem, be sure to read the responses.
The response is listed before the correct one.
The responses can be read in reverse order.
In the "exothermic"/"endothermic" example, pay special attention to the responses that are opposite of each other.
One response may provide a clue as to whether or not both are incorrect.
The first set of responses differed by only one word.
They can give a clue as to how to think about the problem.
Some distracters give answers in which the data are used in the wrong way.
The method used to get the answers is shown in the parentheses.
Keeping in mind that 2, not 5, is the divisor before the proper calculation can be made to obtain answer A, the question hinges on understanding the term divided by and keeping in mind that 2, not 5, is the divisor.
The method for using the data must be understood.
Some common methods for increasing the probability of choosing the correct answer to a numerical chemistry problem are available.
The principle of reasonableness is important.
This means that answers must be in line with fundamental principles.
The reasonableness of answers may be provided by your personal experiences.
If 2 grams of one reactant are mixed with 5 grams of another, it is impossible to have more than 7 grams of product.
Any response greater than 7 grams will be eliminated very quickly.
If a hot solution is added to a cold one, the final temperature must be between the high of the hot solution and the low of the cold solution.
Any other responses may be eliminated without any calculations at all.
The reasonableness of answers will be given throughout the book.
Estimating answers to math problems is important.
The use of calculator is not a focus of the test.
Simple numbers are used in most mathematical problems.
These questions test your ability to set up problems rather than your ability to solve problems or do mathematical operations.
Students need to understand how to estimate rather than calculate answers in accord with this new approach.
The basic principles of estimation are listed below.
There are many problem solutions at the end of the chapters and sample tests that show methods for estimating answers.
The first principle of estimation is that all problems need to be set up in a logical manner.
When calculators were allowed, this has not changed.
Round numbers to one, or at most two significant figures, is the second principle of all estimation.
The third principle is to round in a way that makes it easy to cancel.
Adding and subtracting in groups is the fourth principle.
There are a few examples of these principles.
There are no hard steps to memorize the following.
You should try to round up as much as you can.
You don't have to multiply numbers in sequence.
The calculator answer is 6.24.
When estimating, this is off by 0.24.
The correct answer cannot be 13,248 and it cannot be 10 x 5.
We show how to estimate the high and low limits of a calculation.
The calculator answer is 630.
We chose a single number that could be rounded up or down to find a maximum and minimum, and we rounded it up to find it.
The technique of setting limits on your answers is useful.
The answer is 0.0421.
Again, the estimate is in the ballpark.
Simple math operations were taken advantage of in canceling.
Cancelling saves a lot of work.
The steps were written out above.
These steps are done on a single equation.
The answer is 0.1377 x 10 6 or 1.377 x 10 5.
The answer is 163.8.
Where pH is defined as -log, you can estimate it from [H + ].
For example, 4.1 x 10 -5 M is the hydrogen ion concentration in almost all cases.
A 4.1 x 10 -5 M solution has a pH of 4.39.
The pH is between 4 and 5.
The hydrogen ion concentration has a pH between 4 and 5.
By looking at the power of 10 for the hydrogen ion concentration, we can estimate the pH to within one unit.
A minimum of one pH unit less than the maximum of the positive value is required.
We can quickly say that the pH is between 5 and 6.
The pH is between 10 and 11 if [H + ] is 3.8 x 10 -11.
If you want to know the pOH, we can use the same principle.
The pOH will be between 1 and 2 if the OH is 1.3 x 10 -2 The pOH will be between 5 and 6 if the OH is 3.3 x 10.
The maximum value for the pH or pOH can be found in both cases.
The minimum value that the pH can be is one less than the maximum.
The H + will be 10 -4.7% if you are given a pH of 4.7.
The rules of mathematics do not apply to the decimal exponent.
It's convenient to work with numbers.
The range can be established using a high and a low value.
The [H + ] can be a high of 10 -4 to a low of 5.
The 3.3 x 10 M solution of OH - is estimated.
To get more precision in logarithms, you need to remember that log 2 and log 3 are the same number.
If the OH is 3.3 x 10 -6, we can estimate the pOH as -log, which is 3.3 and -log.
The former is close to zero, and the latter is close to six.
The two add up to more than 5.
Section II of the exam can be used with any scientific calculator.
You should be aware of the operation of your calculator and that the batteries are fresh.
Write the laws that the question requires.
If you use any assumptions, make sure they are valid before reporting the answer.
You should check that you have used the correct number of figures.
Consider the problem of calculating the pH of a 0.100 M solution of hydrofluoric acid.
The equilibrium law, a chemical reaction, and a solution are needed to logically solve the problem.
The assumption is that [H + ] C a is the initial HF concentration.
The exam does not give partial credit.
All work needs to be shown in order to get credit for the question.
If the calculation in the first part is incorrect, the student will be given credit for the later parts of the question.
You won't be given credit for the problem if you don't set up your calculations clearly.
You probably won't get a true essay question.
You will most likely be asked to justify your answer.
You have to answer the question.
The graders don't want to hear about your problem-solving methods.
They want to see how you evaluate your answer.
You can discuss why your answer seems reasonable.
You can compare acid strengths or atomic radii to see if you are thinking beyond the answer.
It is slightly different to justify your answer.
Evidence can be used to show that alternative answers are not as good.
Formal charges are used to defend your choice of structure in relation to other possibilities.
If you don't have to explain or justify your answer, you should ask yourself to answer the questions with each practice problem you work on.
It's important to have enough energy for the exam.
A good dinner the night before and a relaxed breakfast on the day of the exam provide the energy essential to peak performance.
A full 8 hours of sleep is recommended for a rested body and a functioning mind.
The night before the exam is not a good time to cram.
You will need a lot of #2 pencils with erasers, a scientific calculator with fresh batteries, a watch, and your admission card for the AP exam if you want to take it.
You need to plan what you will wear to the test.
It's best to have comfortable, loose-fitting clothes, such as sweaters that can be removed to suit the room temperature.
It's important to make sure your transportation to the test center is reliable.
If you set your alarm, you can leave early.
Allow time to deal with the unexpected: a traffic jam, a flat tire, or a late bus.
Don't worry about your valuables during the test, leave them at home.
All unrelated matters should be put out of your mind.
Successful test taking depends on a positive attitude.
This test will not affect your career.
You can show the world how well you do by taking the exam.
The College Board has an e-mail system that will answer your questions.
The general website can be used to enter the College Board e-mail system.
The AP Chemistry Web pages have a direct URL.
You should check this website for late-breaking news and exam changes.
Information about AP exam registration, sites, test dates and times, score reporting, and fees can be found on this site.
It is important to register on time so that you don't have to pay late- registration fees or miss an exam.
Your AP teacher will guide you through this process.