# Chemistry test 3

 The flashcards below were created by user michaelirby98 on FreezingBlue Flashcards. 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  Empirical Formulas 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 Molecular formula 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/molThen 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) Then convert Authormichaelirby98 ID270326 Card SetChemistry test 3 Descriptionchem Updated2014-04-14T20:43:24Z Show Answers