# Chemistry Primer - Semester 1

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How many squares are in this 2×2 grid (Figure 1)? Note that the figure link lets you know that a figure goes along with this part. This figure is available to the left
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What is the magic number? (Figure 2)
Note that there is a figure also associated with this part. However, the figure for Part A may still be visible on the left. To view the figure associated with Part B, click on the figure link. A new figure should appear on the left.

You could try to guess the magic number but you would probably use up all your tries before getting the answer. Notice the new Hints button above the answer box for this question. Clicking this button will open up a list of hints that will guide you to the correct number.
Multiple-choice questions have a special grading rule. If you determine the answer by process of elimination then you won't get credit. So, if you submit an incorrect answer to a multiple-choice question with n options, you will lose 1/(n−1) of the credit for that question. Just like the similar multiple-choice penalty on most standardized tests, this rule is necessary to prevent random guessing until the correct answer is the last choice remaining.

If a multiple-choice question has five answer choices and you submit one wrong answer before getting the question correct, how much credit will you lose for that part of the question?
A 5.5 g sample of a substance contains only carbon and oxygen. Carbon makes up 35% of the mass of the substance. The rest is made of oxygen.

You are asked to determine the mass of oxygen in the sample.

Which of the following expressions demonstrates a mathematical procedure to solve this problem using the proper order of operations?
A student needs to conduct a reaction that combines chemicals A and B to synthesize product AB. If we write this as a chemical equation it looks like:

A+B→AB

If this student combines 100 molecules of A and 100 molecules of B, the student obtains 100 molecules of AB.

How many molecules of A would this student need to make 5000 molecules of AB? (Assume the student had enough of molecule B to make 5000 molecules of AB.