chemistry paper 1- quantitative + chemical + energy changes Flashcards
How do you find the relative formula mass?
Find the relative atomic masses and add them together
How to calculate the % mass of an element in a compound
Ar X no of atoms of the element
———————————————- X 100
Total of the compound
what us the definition of a mole
an amount of a substance
What is the Avogadro number?
6.02 X 10^23
Formula for the no of moles
Mass in g of Ar
———————————-
Ar of the element
What does it mean by conservation of mass?
During a chemical reaction no atoms are destroyed or created so theres the same number of atoms : no mass is lost or gained.
What happens if mass does increase?
It increases as one of the reactants is a gas
Before the reaction the gas floats around as its not contained, mass cant be determined
When gas reacts to form the product it become contained in the reaction so the mass if the stuff inside the vessel increases
what happens if mass decreased?
Because the product is a gas
Before the reaction all the reactants are contained
If it isn’t enclosed the gas can escape so it wont be contained : you can’t determine mass so total mass decreases of the stuff inside
What happens when a reaction stops?
When one of the reactants gets used up so rest are in excess
Used up reactant = limiting reactant
Why is the amount of product formed directly proportional to the amount of limiting reactant?
Because if you add more reactant there will be more reactant particles to take part in the reaction so more products particles
What does concentration measure?
Measures how crowded things are
Formula for concentration
Concentration = mass of solute
—-——————
volume of solvent
What is concentration measured in ?
g/dm^3
What does a ph of 0-6 mean?
Acids
What does the ph of 8-14 mean?
Alkaline