General chemistry: How to solve problems

Here a few tips on working problems with unit conversions and conversion factors:

(1) Read the questions carefully to be sure of what is being asked.

(2) Unity factors involve two measurements for the same parameter and always equal one. (For example, there are 1000 grams in a kilogram and so to convert from kilograms to grams you must multiply the gram amount by the unity factor 1000 g/1 kg.).

(3) Conversion factors are similar to unity factors, except that they involve at least two different parameters and are even more difficult to work with. (For example, density (g/cm^3) is a conversion factor that can help you convert a volume to a mass (g).

(4) Break up problems into simple steps and write out each step.

(5) For each step, completely write out the units of each number. Then make sure the appropriate units cancel out and that you end up with the same units on both sides of the equal sign.

(6) The last part of a problem should be determining how many significant figures the number should have. To increase your accuracy, do not round numbers up or down until this last step. Also, look back up at the question to double check what is the minimum number of significant figures in any of the numbers.

(7) For volumes, 1 cm^3 = 1 mL is always true.


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