Amount of a substance Flashcards
What is relative atomic mass
Average was of one atom of an element divided by 1/12 mass of 1 atom of C12
What is relative molecular mass
average mass of one molecule divided by 1/12 of one atom of C12
What is relative formula mass
Same as relative molecular mass but used of ionic compounds
What does Avogadro’s constant represent?
The number of particles in a mole
What is concentration of a substance measured in
mol dm-3
What is the formula for the number of moles?
Mass/Mass of 1 mole
What is the equation linking volume, conc., and moles
moles = vol * conc
What is the ideal gas equation
PV=NRT
Pressure in Pa
Volume in m3
Temp in kelvin
How do you calculate the empirical formula
Find masses (g) of each of the elements present in a compound
Find n.o of moles using Mr and masses
Convert number of moles of each element in a whole number ratio
How do you calculate empirical formula from RMM and Percentages
Find percent of each atom in molecule
*
Then divide each answer by the atomic number of the element
*
Divide down to get smallest whole number ratio
What is atom economy
Works out the theoretical mass of product
How do you calculate atom economy?
% atom economy =( molecular mass of desired product / Sum of molecular masses of all reactants ) x 100
What is the percentage yield of a chemical reaction
How efficient the process is and how much loss there is
What is relative isotopic mass
The average mass of an isotope compared to 1/12 the mass of a Carbon 12 atom
What is empirical formula
Simplest whole number ratio of atoms of each element in a compound
What is molecular formula?
The actual number of atoms of each element in a compound
Why is it important to have reactions with high atom economy
*Cheaper as less by products
*Waste chemicals can be harmful to environment
Why don’t actual and theoretical yield match up
Chemicals lost on apparatus
May be gaseous and lost to environment
What is the formula for number of particles
Avogadro’s constant x Number of moles
How does rinsing a burette with distilled water affect titre value
Titre value increases as Burette is more dilute
