- significant figures
- evaluations of analysis
- concentration of calculation
This is a draft cheat sheet. It is a work in progress and is not finished yet.
Reporting Computed Data
- One of the best ways of indicating reliability is to give a confidence limit at the 90% or 95% confidence level.
- Another method is to report the absolute standard deviation or the coefficient of variance of the data.
Rules to Determine the Number of Significant Figures
1. All nonzero digits are significant.
2. An exact number has an infinite number of significant figures.
3. A zero is significant when it is between nonzero digits, at the end of a number that includes a decimal point, before the first nonzero digits, and a trailing zero in a number without a decimal point.
Significant Figures in Calculated Results:
- for addition and subtraction, the number of significant figures can be found by visual inspection.
- for products and quotients, the answer should be rounded so that it contains the same number of significant figures as the original number with the smallest number of significant figures.
- in a logarithm of a number, keep as many digits to the right of the decimal point as there are significant figures in the original number.
- in a antilogarithm of a number, the result should have the same number of significant figures as the number of significant decimal places in the original number.
Stoichiometry and Concentration
Mole Ratio - indicated by coefficients in a balanced equation.
Chemical Reaction - process in which one or more substances is changed into one or more new substances.
Chemical Equation - uses chemical symbols to show what happens during a chemical reaction.
Evaluation of Analytical Data
Mean - arithmetic mean or average.
Median - middle value of a sample of results arranged in order of increasing/decreasing magnitude.
- The median is used advantageously when a set of data contains an outlier. An outlier can have a significant effect on the mean but lesser on the median.
Mode - value that occurs most frequently in a set of determinations.