Useful Chemistry Equations
|% ERROR =
Measurement (or average measurement) – Correct (accurate) measurement
_____________________________________________________________ x 100
Mass (g or kg)
Volume (cm3 or m3- solids and ml or l – liquids)
|PERCENTAGE COMPOSITION =
Mass of part
Mass of whole
MOLS of solute
Liters of solution
MOLS of solute
Mass of solvent in KG
|RATE OF REACTION =
Difference in quantity
Difference in time
Mass in grams
Relative formula mass (atomic mass)
|RELATIVE FORMULA MASS (ATOMIC MASS)=
(Number of atom 1 )(Mass of atom 1) + (Number of atom 2)(Mass of atom 2) + …..
Number of moles
Volume in liters
|NUMBER OF MOLECULES=
Moles of substance X Avogadro’s number
|Wavelength of light emitted from Atom=
Energy of photon (j) = Change in Energy= -Rh (1/n(final) squared – 1/n(initial) squared)
Rh = 2.179*10-18
Wavelength of light emitted = hc/Energy of photon
h = 6.626*10-34 j.s
c = 3*10+8 m/s
(n and m are the coefficients in the balanced equation of the salt dissolving)
|Speed of Gas = 3RT/M
R = 8.31447 J/mol K and M = Molar Mass of molecules and T = Temperature in Kelvin. Answer is in m/s.
Rate of GAS A/Rate of GAS B=
Molar Mass of Gas B/Molar Mass of Gas A
|IDEAL GAS relationship
P.V = n.R.T
P = Pressure in either atm or pa.
V – volume in liters.
n = mols.
R = 0.082 (for atm) and 8.314 (for pa).
T = Temperature in Kelvin.
To calculate the limiting reactant we need to see which molecule is in excess, the other molecule will be the limiting reactant. To do this we calculate the moles of both reactants and compare them to the balanced equation to see which one will be in excess. For all the moles of molecule A to be used up, how many moles of molecule B do we need?
|THEORETICAL AND ACTUAL YIELD
Theoretical yield is the yield in (grams, moles, etc.) that we calculate using formulas. This is the most (maximum) that could be produced.
Actual yield is the yield in (grams, moles, etc.) that is really produced.
|HEAT OF A REACTION
To calculate the heat of a reaction using bong energies use this:
|TYPE OF BOND
To calculate the type of bond use this:
If the answer is between 0 and 0.3 it is a non polar covalent bond.
If the answer is between 0.3 and 1.7 it is a polar covalent bond.
If the answers is between 1.7 and 3.5 it is an ionic bond.
Any values that is on the borders can be either, or something in between (remember science is an approximation).
When K is bigger then 1 we say that the products are favored. When K is around 1 we say that neither one side is favored. When K is less then 1 we say that the reactant side is favored.