Formula Sheet
Formula 1: Moles to Atoms
Given
Find
Formula/Steps
Moles To Atoms Take the number of moles given times 6.02 x 10 23
divided by 1 mole= # of atoms.
#moles given x 6.02 x 10 23 = # of Atoms ______
1 mole
Formula 2: Atoms to Moles
Given
Find
Formula/Steps
Atoms to Moles Take the number of atoms given ( put in
parenthesis) times by 1 mole and divide by
(6.02 x 10 23) atoms = # of moles _____
(#of atoms given) x 1 mole = # of moles ___
6.02 x 10 23
Example Problem
How many atoms are present in 3.7 moles of Na?
3.7 moles Na x 6.02 x 10 23 = 2.228 x 10 24 atoms Na
1 mole
[Sig Figs 3.7 = 2]
Answer is 2.2 x 10 24 atoms Na
Example Problem
How many Moles of Silver are in 3.01 x 1024 Atoms
(3.01x 1024) atoms Ag x 1 mole
= 0.5 mol Ag
23
(6.02 x 10 )
[Sig Figs 3.01= 3]
Answer is 0.500mol Ag
** Atoms, Molecules, Formulas Units and Representative Particles are all the same and you use the above equations.
Formula 3: Calculating Molar Mass/Macular Weight/Formula Mass
Formula/ Steps
1. Find the number of each atom in the compound.
2. Multiply each atom by its mass on the periodic table.
3. Add up all the masses of the atoms.
4. Units are g/mole
Example Problem
Find the molar mass of SO2
Step 1 & 2. Find the number of atoms of each element and mass of
each element
#Atoms x Mass = Total
S = 1 x 32 = 32
O = 2 x 16 = 32
Step 3 Add up the total atom mass = 64 g/mole S)2
2 conversion factors
1 mole = 6.02 x 1023 atoms
1 mole = molar mass of element or compound
Formula 4 Mole to Mass
Given
Find
Formula/ Steps
Mole
To Mass
# of Moles given times molar mass of element or compound
divided by 1 mole = the number grams element or compound
# moles given x Molar Mass of elements or compound = # grams element
or compound
1 mole
Example Problem
Mole to mass
Given
There are 2.50 moles of sodium chloride.
Find
How many grams does this form?
3
calculated
2.50 moles of NaCl x 58.5glmoNaCl = 146gNaCl
1 mole
Na = 1 x 23 = 23
Cl = 1 x 35.5 =35.5
= 58.5 g/mol NaCl
Formula 5 Mass to Moles
Given
Find
Formula/ Steps
Mass
To Moles Number of grams given times 1 mole divided by molar mass of
element or compound equals number of moles element or
compound
#grams given x 1 mole
= #moles element or compound
Molar mass
Of element or compound
Example Problem
Mass to Moles
given
A chemist produced 11.9 g of Aluminum from its ore.
Find
How many moles of Aluminum has been produced?
3 sig figs
11.9g Al x 1 moles = 0.441 mole Al
27.0 g Al
2 step problems
Formula 6 Mass to atoms
Formula/ Steps
Mass
To Atoms Step 1
#grams given x 1 mole #moles element or compound
Molar mass
Of element or compound
Step 2
#moles given x 6.02 x 10 23 = # of Atoms ______
1 mole
Example Problem
Mass to Atoms
Calculate the number of molecules given 5.4g of Zinc
Step 1 (mass- mole)
5.4 g Zn x 1 mole Zn = 0.82 mol Zn
65.4 g Zn
Step 2 ( Mole – Atom)
0.82 mol ZN x 6.02 x 10 23 Atoms
1 mole Zn
Formula 7 Atom – Mass
Formula/ Steps
Atom To MASS Step 1 Atoms to Moles
(#of atoms given) x 1 mole = # of moles ___
6.02 x 10 23
Step 2 Moles – Mass
# moles given x Molar Mass of elements or compound = # grams
1mole
element or compound
= 5.0x1023 atoms Zn
Example Problem
Calculate the grams of Calcium given 3.4 x 10 24 atoms of
Calcium.
Step 1 Atoms to Moles
3.4 x 10 24 atoms Ca x 1 mole Ca = 5.6 mol Ca
6.02 x 10 23 atoms
Step 2 Mole – Mass
5.6 molCa x 40.1 g Ca = 224.56g 2 sig figs = 220 g Ca
1mole Ca
1 mole = 22.4 L (Liters)
STP = Standard temperature and pressure
STP Temperature = 0 ◦ C STP Pressure 1 atm
Formula 8 Moles to Volume [L]
Formula/ Steps
Moles To volume # of moles given x 22.4 L = # of Liters
1 mole
Formula 9 Volume[L] to Moles
Formula/ Steps
Volume To Moles # of Liters given x 1 mole = # of Moles _____element or
22.4 L
compound
Example Problem
Moles to volume
given
A chemical reaction produces 0.37 moles of N2 gas.
Find
What Volume will that gas at STP?
0.37 moles N2 x 22.4 L = 8.288 L N2
1 mole
2 Sig Figs = 8.3 L N2
Example Problem
Volume to Moles
given
A container with a volume of 893 L contains
Find
How many moles of air at STP?
893L air x 1 mole = 39.86 moles air
22.4L
3 sig figs = 39.9 moles air
Formula 10 Percent composition
Formula/Steps
Percent Composition
Step 1: Find the molar mass of the compound.
Step 2: Divide each element in the compound by the molar mass
of the compound.
Step 3 multiply by 100 to get a percent.
Formula for step 2 and 3
Mass of element
x 100 = % of element
Molar mass of compound
Example Problem
Percent Composition
Find the percent composition of
Copper (I) sulfide, Cu2S?
Formula  molar mass  % of each element
Step 1: Find the molar mass of the compound.
Atoms
Mass
Total
Cu
2
63.546
127.09
S
1
32.06
+32.06
159.15 g/mol Cu2S
Step 2: Find the % composition.
Cu = 127.09  100 = 79.855% Cu
159.15
round to – 79.86% Cu
S = 32.06  100 = 20.14 % S
159.15
Reminder: The sum of the elements has to equal 100%.