1.3 Chemical Calculations Flashcards
How do you work out the number of moles using mass?
number of moles = mass/mr
How do you work out the number of moles using concentration?
number of moles = concentration x volume
In what units should volume always be in?
dm^3
What is the unit for concentration?
mol dm^-3
What is mr?
relative atomic mass
How do you work out the empirical formula?
mass of the substances
divided by it’s mr
divide again by the lowest
work out the ratio
What is the ideal gas equation
PV= nRT
What does P stand for in the ideal gas equation? units?
pressure (Pascals/Pa)
What does V stand for in the ideal gas equation? units?
Volume (m^3)
What does n stand for in the ideal gas equation? units?
moles (mol)
What does R stand for in the ideal gas equation?
molar/ideal gas constant
always 8.31
What does T stand for in the ideal gas equation? units?
temperature (Kelvin/K)
How do you convert from *C to Kelvin (temperature)?
+273
How do you convert cm^3 to dm^3?
divide 1000
How do you convert dm^3 to m^3?
divide 1000
How do you convert m^3 to dm^3?
divide 1000
How do you convert dm^3 to cm^3?
x 1000
How do you convert cm^3 to m^3?
divide 1000000
How do you convert m^3 to cm^3?
x 1000000
How do you work out the atom economy?
(mass of useful product / total mass of reactants) x 100
What is the unit of atom economy?
%
How do you work out the molecular formula?
Divide the molar mass by empirical formula molar mass
then multiply that number by the empirical formula
how do you calculate a back titration?
- Calculate the moles of acid added
- Calculate the moles of alkali added
- Subtract the moles of alkali from the moles of acid to give the number of acid reacted
- Calculate the moles of base that reacted
- Calculate the mass of base reacted
- Calculate % mass (mass reacted/mass of tablet x 100)
How do you work out percentage yield?
mass of required product/theoretical x 100
