Stoich Test Flashcards
(42 cards)
How to find the formula or molecular mass?
Add up all the individual masses of the elements `
Units for formula/molecular mass
amu
What does S.T.P stand for
Standard temperature and pressure
Mass spectrometer
used to compare the masses of atoms
the amount of deflection by a magnet is measured
the most massive are deflected the smallest amount
what are the amu masses on the periodic table?
averages of all the isotopes
What does the mole techinically equal?
the number of carbon atoms in exactly 12g of carbon
What else can particles be called?
Formula units
molecules (not MOLES)
atoms
Does it matter the element for how many moles there are?
No
No matter what elements there are an equal number of atoms in each mole
Like saying a dozen of something (could be eggs or cookies)
Difference between formula/molecular mass and molar mass?
Molar mass is in g/mol
Molecular mass is in amu
Difference between 1 and 2 step stoich problems and 3 step stoich problems
3 step you need to cross the mole bridge and involve more types of molecules than just one
How would I solve:
how many grams of copper chloride is needed to react with 160 grams of aluminium?
3 step mole problem
cross mole bridge
do NOT do limiting and excess reagents since you are only given 160 grams
How would I solve:
What volume of ammonia at STP is produced when 25 g of nitrogen reacts with hydrogen?
3 step mole problem
cross mole bridge
do NOT do limiting and excess reagents since you were only given 1 number
Stoichiometry
the study of the quantitate relationships that can be derived from chemical equations
Why use stoichiometry?
Allows scientists to accurately predict amounts of reactants and product before a reaction occurs
Limiting reactant
the reactant in a chemical reaction that limits the amount of product that can be produced
When does a reaction stop?
When all the limiting reactant is consumed
Excess reactant
the reactant in a chemical reaction that remains when a reaction stops
always has leftovers because the limiting reactant ran out
How would I solve:
Identify the limiting reactant when 3.0g of H2 and 32g of O2 react to produce water
Get the equation
solve a limiting reactant problem
can tell since it gives two gram measurements and asks for limiting reactant
% Yield
actual/theortical *100
% Accuracy
experimental-theortical/theoritical *100
How would I solve:
What is the concentration of the solution if you dissolve 0.25 moles HCl of 0.5 L of solution?
Molarity problem
Take moles/liters
Can tell through keyword “concentration”
What is the molarity formula?
Moles/liters
How would I solve:
How many moles of 5 liters of a 3M NaOH solution?
5L is flying solo by itself and has to be multiplied by 3moles/L (which is the molarity)
This will cancel out the liters and then your good
Remember: in molarity conversion volume flys solo
How would I solve:
How many grams of sodium hydroxide are necessary to make 500mL of a 0.5M concentrated solution?
Molarity conversion
1) Convert mL to L
2) L flys solo
3) Multiply L by moles/L (M)
4) Get to grams by multiplying by grams/moles
