exam one [chapters one through three] formulas

density formula

D=M/V

molar mass

mass A ~> moles A

balanced chemical equation

moles A ~> mass B

molar concentration formula

M = mol solute/ L solution

molecular or molar mass [in amu or g/mol] / empirical formula mass [amu or g/mol] = n formula units/molecule

derivation of molecular formulas [what’s the formula to get n formula units/molecule]

volume

V=moles solute/M [molarity]

dilution equation

C₁V₁ = C₂V₂

mass percentage

mass percentage = mass of component/mass of solution ∙ 100%

accuracy: absolute error

| average expected value - Actual value |

ACCURACY % error

% error = (absolute error [ |avg exp - actual| ] ÷ actual value) • 100%

[you need abs error to get % error]

i.e.

avg of trials = 8.74

actual = 8.96

abs error = |8.74-8.96| = 0.22

% error = 0.22 ÷ 8.96 [actual] = 0.025 • 100% = 2.5%

PRECISION deviation

deviation = | experimental - avg |

PRECISION % deviation

% dev = avg dev [must know deviation and avgs] / avg value • 100%

atomic mass

average weighted mass considering isotopes

atomic number

defines number of protons [number at top of element in the periodic table]

mass #

protons plus neutrons — total number of both added

[i.e. I-127 and there are 53 protons —> 127-53=74 and 74 equals the number of neutrons