quantitative chemistry Flashcards
conservation of mass
sum of mass of reactants = sum of mass of products
amu
atomic mass unit
2 elements combine
-ide
more than 2 elements combine
-ate
2 or more atoms of same element
no change
what does iron (II) mean
indicates charge on transition metal. fe 2+
ionic compounds and charge
no overall charge - total positive charge = total negative charge
hydroxide
OH-
carbonate
CO3 2-
zinc
Zn 2+
nitrate
NO3 -
ammonium
NH4 +
lead
Pb 2+
sulfate
SO4 2-
copper
Cu 2+
silver
Ag+
relative atomic mass
mean average mass of an atom of an element expressed in AMU
how to calculate relative atomic mass with percentage abundance
(M1 * 0.P1) * (M2 * 0.P2) = RMA
relative formula mass
sum of all atomic masses present in the formula (Mr)
relative molecular mass
sum of all atomic masses present in the formula (Mr)
percentage by mass
RFM of wanted element / RFM
why are moles used?
different chemicals contain different atoms -> mass cannot be used to compare particles easily
what is avagadro’s constant
6.02 * 10^23
what is the equation for moles
n = number of particles (mol)
Mr = relative formula/molecular mass
m = mass in g
n * Mr = m
how were equations made before the periodic table?
- evidence for a formula had to be worked out using practical methods
- ratio between reactants and products could be found by experiment
- dalton’s atomic weights meant chemists could calculate ratios of particles
- moles = numbers of particles (for us)
what is an excess of a chemical
having more of a chemical than required for a reaction
which is the limiting reactant
the chemical that is completely used up first
do you use the mass of the reactant in excess
no - only the mass of the limiting reactant
how is the limiting reactant calculated
you have 2.4g of Mg and 2.0g of O2
2mg + 02 -> 2MgO
1) 1 O2 + 2 Mg -> 1 MgO
0.0625 * 2 = 0.125 moles of mg
0.1 moles of Mg and up to 0.125 of O2 present, excess of O2 and Mg is limiting
solution
mixture of a solute and solvent
solute
a soluble solid that dissolves in a solvent
saturated solvent
no more solute can dissolve in the solvent
what is concentration
quantity of solute / quantity of liquid
what is the measurement of concentration?
1) grams per cubic decimeter
g/dm^3
2) mol per cubic decimeter
mol/dm^3
how do you convert from cubic centimeters to cubic decimeters
divide by 1000
how do you convert from cubic decimeters to cubic centimeters
multiply by 1000
