Calculator Practice for Chem 1B
Calculator Practice for Chem 1B
One significant issue in Chem 1B is that a subset of students do not know how to do some basic algebra. This is made worse by incorrectly using a calculator to try to do the algebra. The students then ask an instructor during a quiz or exam to help them with their calculator. We can't help you. You must know how to use your calculator. Some borrow calculators from us during quizzes and exams and don't know how to use them because they are not like the one they use at home. So try the problems below with YOUR non-programmable calculator to make sure you correctly know how to use it. Try the worksheet for more practice. Then bring that calculator with you to lab, seminar and lecture, because you will be solving math problems like this during the classes, quizzes, report sheets and exams.
If you do not have a nonprogrammable calculator, as was required for Chem 1A, then I encourage you to purchase one. You will use it a lot in Chem 1B, since Chem 1B has a lot more math than Chem 1A. A good choice is a TI-30Xa. Staples has them for around $13.
As a first example, (1/8) + (1/5) does not equal 2/13, nor 2/40. It equals 0.325, or 13/40, if left as a fraction.
Try the ones below using your calculator to see if you get the correct answer.
1) (1/298) - (1/345) = ? This type of math is associated with activation energy in the topic of kinetics.
Correct answer is 4.6 x 10-4 and it only gets two sig figs. so review sig figs if you do not know why. It is a subtraction.
2) Logarithms and natural logarithms are used in Chem 1B in kinetics, equilibrium, acid base chemistry, electrochemistry and nuclear chemistry. Sig figs for logarithms will be explained when you cover pH in Chem 1B.
log (4.3 x 10-5) = ? Correct answer is -4.37
ln (2.4 x 102) = ? Correct answer is 5.48
3) Inverse log and inverse ln are used for the same topics as those listed in 2)
ln x = -2.55 What is x? Correct answer = 0.078 of 7.8 x 10-2
log y = 8.44 What is y? Correct answer = 2.8 x 108
4) Calculations with scientific notation are part of the full course. They will show up a lot in kinetics and equilibrium.
(1.1 x 10-5) (2.1 x10-6) / 4.4 x 10-3 = ? Correct answer is 5.3 x 10-9
5) Combining some of these to solve a problem. These are sample kinetics calculations that you might need to solve in an exam.
ln (x/.30) = - (2.4 x 10-4) (4.5 x 103) What is x? Correct answer is 0.10
[(1/y) - (1/0.50)] = (3.3 x10-2) (55) What is y? Correct answer is 0.27
ln (7.7 x 10-5/4.3 x 10-4) = (-z / 8.31) [(1/298 - (1/345)] What is z? Correct answer is 3.1 x 104
6) Raising numbers to exponents (squaring, cubing, etc.) is important for the subject of solubility.
(3x)3 = ? Correct answer is 27 x3
(3.0 x 10-3)3 = ? Correct answer is 2.7 x 10-8
(0.20) (3x)3 = 5.4 x 10-13 What is x? Correct answer is x = 4.7 x 10-5