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0.1 I Can Count

0.5 Basic Math/Algebra

# Basic Math/Algebra

So yes, we do expect you to be able to do basic math and algebra. We will not make you do calculus or differential equations - just some plain ol' algebra. This means you might memorize an equation with some variables in it and we tell you a few of them - then you calculate for the missing one. Here is an example and the solution...

#### gas law type question

A given sample of an ideal gas at 300 K occupies 20.2 L at a pressure of 1.50 atm. How many moles of gas are in this sample?

Solution: Use the ideal gas law! $$\longrightarrow PV = nRT$$

Now put in all the known values ($$P,V,T,R$$) and solve for the unknown value ($$n$$).

$(1.50\;{\rm atm})(20.2\;{\rm L}) = n(0.08206\;{\rm L\;atm/mol \,K})(300\;{\rm K})$

${(1.50)(20.2)\over (0.08206)(300)} = n$

$1.23\;{\rm mol} = n$

Not too bad, right? 1.23 moles of ideal gas is the answer and we just substituted into the equation and then did a little algebra to solve. You might get longer questions to solve - meaning more numbers and math... but, it will not be harder algebra. Just don't get lost along the way to the answer.

In the above example I dropped all units after the first line. The units DO work out to end up with only moles for the units of $$n$$. Sometimes I drop units in examples in order to show the pure math and not let units clutter my page. You might want to drag the units along for the ride though - in case you get lost. Units will often help lead you to the right way to do the math.