Chemistry test 3

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Chemistry test 3
2014-04-14 16:43:24
chem test 3
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  1. 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
  2. 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
  3. Steps to get from grams of a substance to number of atoms
    • Grams to mole,
    • Moles to atoms (avogardos number)
  4. Equation for precent composition
    Percentage = Part/whole X 100
  5. 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 

  6. Empirical Formulas
    The simplest whole number ratio of atoms in a molecule

    H2O2 -> HO
  7. 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
  8. Molecular formula
    A multiple of the emp formula

  9. 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
  10. 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
  11. 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 O= 4.30mol C3H= 5mol O2)

    Then convert