Chemistry test 3
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How to find the amount of moles of 10.0g of AL
(Grams of AL)(1mol/amu in grams) = Moles
10.0g)(1 mol/ 26.89g)= 0.37064
How to find amount of atoms in a specified amount 10.0g of AL
First convert 10.0g into mol = .37064 then find amount of atoms with avagadros number
(.37064mol AL)(6.022X1023/1 mole AL)
Keep number in scientific notation
Steps to get from grams of a substance to number of atoms
- Grams to mole,
- Moles to atoms (avogardos number)
Equation for precent composition
Percentage = Part/whole X 100
How to find percent composition of carbon in C2H5OH
- Percent = Part/whole X 100
- First find the amu of the entire compd (46.068g/mol)
- Multiple C by number of
The simplest whole number ratio of atoms in a molecule
H2O2 -> HO
How to calculate empirical formulas from percent compositions?
Do this for all compositions, then divide all #s by the lowest amount of moles.
Multiply numbers by 2 or 3 to get whole numbers
A multiple of the emp formula
How would you find the molecular formula of 252g of C5H3 ?
- Find the mass of the 5C and 3H = 63.074 g/mol
- Then divide is with the mass you have.
then multiply emp1rical form by 4
How would you find molecular formula from percent compositions?
ex %49.47C, 5.191%H, 28.86%N, O, molec mass of 194g
- Make the %comp into grams.
- Divide that by elements amu
then you would divide that by the smallest amount of grams/mol
Determining amount of moles formed/ needed when reacting
- First you need to balance the equation.
- Then you use equivalence factors (4.30 moles of C3H8 and O2 = 4.30mol C3H8 = 5mol O2)
What would you like to do?
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