The KUDO,S method of solving chemical problems

Have you ever used the KUDOS method to solve chemistry word problems? For any chemistry problems that involve calculations, approach them as solving math problems with unit consideration.

Note: Today's tip is a big longer than usual, since I want to take the time to explain how you solve chemistry problem effectively. This is one of most challenges students face.

Here is my simple five-step K-U-D-O-S method for solving chemistry word problems:

Step 1: "K"nown
Read the problem carefully in its entirety. Write down what is given, translated into mathematical form with units. For example, "The reaction occurs at STP" becomes, "P=1 atm, and T=273.15K" (since STP stands for standard pressure and temperature). Look for implied relationships too. If a 100 grams of binary compound AB is 25% by mass for element A, this implies that there is 75% or 75g in B.
If a reaction is involved, write out the chemical equation and don't forget to balance it.

Step 2: "U"nknown
Write down the unknown in the mathematical form: For example, V=? ml. Complete the equation with the unit you are seeking to make clear what to solve in the problem.

Step 3: "D"efinition
Define the physical equation or formula that relates the unknown quantity to the known quantities (PV=nRT). Rearrange the equation so that the unknown is alone on the left side and all the known quantities are on the right side.

Check to make sure you have sufficient data for the selected equation. If not, look elsewhere. Some might require you to get the values from a table of data or the Periodic Table. Again, write them down with the units.

Often, the solution to a problem will involve the use of two or more equations. Solve these symbolically first, before going to Step 4 and entering data. Alternately, you could also plug in the data to solve one equation at a time. Show all the algebra steps clearly for full credit.
If you still don't have enough known data for the defined equation, you might want to use a different equation, or the same equation in a different form.

Step 4: "O"utput
Perform the calculation or derivation to output the result (the Unknown). Plug in the Knowns. These include the constants needed with the proper units and the conversion factors that convert all known quantities needed to proper units required for the equation. Put everything together and solve the equation. Plug in all the known quantities and constants with the units. Calculate the results and run the dimension analysis to assure the proper end unit of the answer. State the answer clearly with its unit and proper significant figure.

Step 5: "S"ubstantiation
Substantiate your result (Output) with a 1-2-3 Check:
- Check its validity.
- Check its unit.
- Check its significant figures.

The KUDOS method is a systematic, yet simple approach. I have created a step-by-step problem solving template for you to fill in the blanks and follow through. The Chemistry Survival Guide also provides an illustration of how to solve a typical chemistry problem using the KUDOS template. In addition, I have create an 20-minute movie to explain this problem-solving method, example after example, until you GET IT. It is available from our chemistry coaching students.

Chemistry problems have patterns, so solving them requires a system to identify and follow these patterns. The KUDOS method introduced here will allow you to unlock the patterns in a logical sequence.

KUDOS to you for reading this article in its entirety. Until next time, give your homework and exams a KUDOS!