Flashcards in C3 Quantitative Chemistry Deck (25):
How do you work out the relative atomic mass of a molecule, substance?
eg Find the relative atomic mass of MgCl2
(the 2 is meant to be little)
Mg= 24 Cl= 35.5
You look up the relative atomic masses of each of the elements in the compound then add them together.
24 + ( 2*35.5)= 95
So the Mr = 95
How do you find the percentage mass of an element in a compound?
Percentage mass of an element in a compound
( Ar* number of atoms of that element/ Mr of the compound) times 100
Ar= atomic mass of the individual element
Mr= the relative atomic mass of the whole compound
What is a mole?
The name given to an amount of substance.
What is Avogadro's number?
6.02* 10 (23, power) particles
How do you find the number of Moles in a given mass?
Number of moles=
mass in g (of an element or compound) / Mr (of element or compound)
What is the equation for mass?
number of moles* Mr
How do you find the Mr
Mr= mass/ number of moles
What is the rule for atoms in a chemical reaction?
What does this mean about the atoms on each side of the equation?
No atoms are created or destroyed.
The same number of atoms of each element should be on both sides of the equation.
What is the rule for mass in a chemical reaction?
No mass is lost or gained.
If the mass seems to change, why?
There is a gas involved
When do reactions stop?
What are the other reactants classed as?
When all of one of the reactants is used up.
They are excess
What is the reactant used up in a reaction called?
The limiting reactant.
How do you measure concentration?
Concentration= mass of solute (g)/ volume of solvent (dm3)
What is the triangle for concentration?
concentration Volume (to remember it)
concentration makes victory
What is concentration measured in?
What is mass measured in?
What is volume measured in?
What is concentration a measure of?
How crowded things are.
If there is more solute than a given volume, what is the solution?
The solution is more concentrated.
What is an isotope?
An atom with a different number of neutrons.
What is the relative atomic mass of an element ?
It's the average mass of an atom of the element compared to the mass of an atom of carbon -12
How do you find the RAM (relative atomic mass)?
RAM= (isotopic mass* % abundance) + (isotopic mass* % abundance) / 100
What is a mole?
The relative atomic mass of a substance in grams.
What is the mole of water?
6.02 * 10 (23, power form) molecules