chem 30 march test
theoretical yield
maximum amount of product that can be produced from a given amount of reactant.
percent yield
actual yield/theoretical yield x100
percent error
actual yield-theoretical yield/theoretical yield x 100
actual yield
amount of product actually produced when the chemical reaction is carried out in an experiment
avagadros law
at constant temp and pressure, the volume of a gas is directly proportional to the number of moles. equals volumes of gases, or the same temp and pressure, have equal molecules of gas particles.
molar volume
one mole of any gas at STP has a volume of 22.4L. the molar volume of a gas at 25C and 1atm is 24.5L.
density at stp
MM/MV=MM/22.4L=M/V
ideal gas law
PV=nRT or V=nRT/P. or n=PV/RT
density using ideal gas law
n/V=P/RT
density in g/L
moles/liter x grams/mole = grams/L, therefore d= p(mm)/rt
how is gas collected and is the end result pure
gas is often collected by displacement of water, in an apparatus. hydrogen is not pure when doing this bc it is mixed with water vapor.
what happens to vp with increasing temps
vapor pressure increases with increasing temp because higher temps cause more water molecules to evaporate
determine partial pressure of gas produced
to determine partial pressure of gas produced, the total pressure measured in flask must be corrected for vapor present, like Pt=Ph2+Ph2o, Ph2=Pt-Ph2o
sequence for stoichiometry
p,v,t of gas a- amount a in moles- mol ratio- amount b in moles- p,v,t of gas b
at constant volume, what happens to total pressure
if volume is kept constant and nothing has been added to the mixture, the total pressure decreases over the course of the rxn bc fewer particles
when can coefficients be read as volumes
the coefficents can also be read as volumes if the gases react at the same t and p
what do all physical and chemical changes do
all physical and chemical changes release or absorb energy.
ex. ice- water (heat absorbed)
ex. ch4+o2 - co2+h2o+heat (heat released)
endothermic
heat absorbed is endothermic
Heat(KJ) + A + B = C
heat of equation (ΔH) = +
exothermic
heat released is exothermic
A + B = C + Heat(KJ)
heat of equation (ΔH) = -
unit used for energy
Joule
thermochemical equations
thermochemical equations show reactants, products, and energy