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Cheat Sheet

Chemistry Workbook For Dummies

From Chemistry Workbook For Dummies by Peter J. Mikulecky, Katherine Brutlag, Michelle Rose Gilman, Brian Peterson

Getting through a chemistry class involves using a range of different science skills and procedures: You analyze atomic structure, work with formulas, name compounds, use scientific notation, and balance chemical equations. Is there anything you don't do in chemistry?

Basic Exponential and Scientific Notation for Chemistry

In chemistry, you often use exponential notation, which is simply using exponents to express a number. Scientific notation is a specific form of exponential notation that uses powers of 10, and numbers between 1 and 10, written as follows, where A is between 1 and 10 and B is an integer:

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Measurements have only a certain amount of precision. When you do calculations with measurements, you must make sure that your answers suggest no greater precision than was present in the original measurements:

  • For addition and subtraction, use exponential notation to express both numbers using the same power of 10. Then round the sum or difference to the same number of decimal places as held by the measurement with the fewest decimal places.

  • For multiplication and division, express both numbers in scientific notation so it's clear how many significant figures each number has. Round the product or quotient to the same number of significant figures as held by the measurement with the fewest significant figures.

Analyzing Atomic Structure for Chemistry

Chemistry deals with atoms, which are composed of subatomic particles, which differ in mass and charge. Altering the numbers of these particles can alter the element or isotope identity of an atom. The following list shows some subatomic facts:

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Key Chemistry Formulas

In chemistry, you deal with all sorts of substances in all sorts of stages — solid, liquid, and gas. The following list offers some key equivalencies and often-used chemistry formulas:

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How to Name a Chemical Compound

Someone who doesn't know chemistry might think that compounds should already have names, but you know differently. The following steps take you through the process of building a chemical name, using compound XAYB as an example:

  1. Is X hydrogen?

    If so, the compound is probably an acid and may use a common name. If X isn't hydrogen, proceed to Step 2.

  2. Is X a nonmetal or a metal?

    If X is a nonmetal, then the compound is molecular. For molecular compounds, use numeric prefixes before each element's name to specify the number of each element. If there's only one atom of element X, no prefix is required before the name of X. Use the suffix –ide after the element name for Y. If X is a metal, then the compound is ionic; proceed to Step 3.

  3. Is X a metal that has variable charge?

    If X has a variable charge (often, these are group B metals), you must specify its charge within the compound by using a Roman numeral within parentheses between the element names for X and Y. For example, use (II) for Fe2+ and (III) for Fe3+. Proceed to Step 4.

  4. Is Y a polyatomic ion?

    If Y is a polyatomic ion, use the appropriate name for that ion. Usually, polyatomic anions have an ending of –ate or –ite (corresponding to related ions that contain more or less oxygen, respectively). Another common ending for polyatomic ions is –ide, as in hydroxide (OH) and cyanide (CN). If Y is not a polyatomic ion, use the suffix –ide after the name of Y.

How to Balance a Chemical Equation

When you balance equations in chemistry, you change only the coefficients in front of the chemical symbols. Never ever change the subscripts in the chemical compounds. The following steps show the balancing process:

  1. Add up the number of each kind of atom on the reactants side and the products side of the chemical equation.

  2. Use coefficients in front of each compound to balance the number of each kind of atom or polyatomic ion, one at a time.

    This may take some trial and error, going back and forth from the reactants side to the products side. For simplicity, start by balancing the kind of atoms or polyatomic ions of which there are the fewest number.

  3. Check the equation to make sure each kind of atom or polyatomic ion is balanced.

  4. Put the balanced equation into lowest terms.

    In other words, if you can divide all the coefficients evenly by the same positive integer, then do so.

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