chapter 7 Flashcards
define chemical formula
the molar ratio of atoms within a compound. subscripts show the molar ratio of atoms in stable compound.
ex: NaCl(formula unit) CH4- 4mol H/1 mol CH4(molecule)
define chemical equation
the molar ratio of compounds within a balaced chemical equation. coefficients show the molar ratio of compounds in a balanced reaction (law of conservation of mass)
define percent composition
the percentage by mass of the constituent elements of a compound with respect to the total mass
describe percent composition
if given molecule and molar mass, divide individual element molar mass by the molar mass of the compound ans multiple by 100 making a percent.
if given elemental analysis (percents of each element) then do in terms of 100 g. take g amount of element percent and divide by mass of element and get answers. divide by the lowest answer and try to get whole # for empirical formula
how to find molecular formula
do empirical formula then divide given amu(g/mol) by empirical formula molar mass and mulitple the result by the empirical formula
define theoretical yield
how much you can make
define limiting factor
what runs out first therfore it determines the theoretical yield
describe process of determing the limiting factor and theoretical yield : “what mass of H2O(g) can be produced when reacting 4.00g CH3NO3 and 3.00 g O2?”
set up the rxn and balance it. take your given grams separately and convert to mols by diving by molar mass. then do the molar ratio based on the balanced equation(x H2O/x mol) then multiple by molar mass of H2O so answer is back in grams. lowest answer is the theoretical yield and that given molecule/elemnt is the limiting factor while the other given is “in excess”
describe a combustion analysis
can either be a carbohydrate(CHO) or hydrocarbon(CH). take given CO2 g and H2O g and use those as givens. seperatly divide by their molar mass then do molar ratio of x mol C/x mol CO2 or x mol H/x mol H2O. get your answers. do empircal formula and molecular formula if given amu/ g/mol
describe percent yield. problem will say ex: 3.4 g Na w/ excess Cl, produced 2.4 g NaCl.
% yield= (actual/theoretical) x 100.
write out balanced equation.
do given divided by molar mass times molar ratio of 1 mol NaCl/ 1 mol Na then multiple by molar mass of NaCl and get answer.
2.4 g NaCl/ answer you got × 100= your percent yield%
