Chemistry test

Percent error

|experimental - theoretical | / theoretical multiplied by 100

accuracy vs precision

correctness vs consistency

solution and its two parts

Solution: uniform mixture consists of solute and solvent

Solute: substance that gets dissolved

Solvent: liquid / substance that does the dissolving

isotopic notation

top # = mass # aka # of protons + neutrons

bottom # = atomic # aka # of protons (number on the periodic table)

Sig-figs

Zeros only sig fig if: sandwich or right-right (right of a decimal and sigfig)

Addition/Subtraction: round to least amount of decimal places

Multiply/Divide: round to least amount of sigfigs

Scientific notation 10^ doesn’t count for sigfigs

intensive vs. extensive properties

intensive: do not change no matter how much of the substance you have; ex. color, temperature

extensive: change depending on size/quantity of sample; ex. volume, weight, length

physical vs chemical properties

Physical properties: observed and measured w/o changing chemical identity of sample; ex. color, length, volume

Chemical properties: observed and measured as sample changes chemical identity; ex. flammability, reactivity

how to calculate weighted average atomic mass

Multiply the relative percentage of each isotope by its molar mass then add all the masses up

how to calculate percent abundance

1. one isotope percentage = x, other isotope percentage = 1-x

2. X (Molar mass of Isotope A) + 1 -x (Molar mass of Isotope B) = WAAM (periodic table mass)

3. solve for x and multiply by 100

how to calculate empirical formula

1. turn percentages into mass unless actual masses are given

2. find molar masses of elements

3. convert #1 masses to moles using molar masses

4. divide all elements by smallest # of moles

5. check answer w/ percent composition

how to calculate molecular formula

1. find empirical formula

2. find molar mass of empirical formula

3. find whole # multiple by dividing empirical formula molar mass / molecular formula molar mass (given)

4. multiply empirical formula by whole # multiple → molecular formula

deliquesce

when the dry chemical absorbs moisture from the air and begins to look ‘liquidy’

efflorescence

when hydrates lose water to the atmosphere

periodic table families

Leftmost: alkali

Second most left: alkaline earth metals

Second most right: halogens

Most right: noble gases