Stoichiometry theory Flashcards
What is relative atomic mass (Ar)
It is the average mass of an atom of an element relative to the 1/12th of mass of an atom of c-12 isotope
Formula for relative atomic mass
Mean mass of an element÷ 1/12th of the mass of an atom of C12
What is relative molecular mass (Mr)
It is the average mass of a molecule relative to the 1/12th of mass of an atom of C-12 isotope
How can relative molecular mass be calculated?
By adding relative atomic mass values of atoms in the molecule
What is relative formula mass?
Similar to relative molecular mass.
When molecules are associated with water of crystallization the term formula mass comes into play
What is molar mass?
Molar mass is the mass per mole (mass of 1 mole) of any substance
What is the unit for molar mass ?
Grams/Mol
What is the formula to calculate number of moles
n=m/M
n= no of moles
m= mass of substances
M= Molar mass of substance
Unit Is mol
What is avogadros constant?
It is the number of particles in one mole of a substance
What is the numerical value of avogadros constant?
6.02×10^23
How are moles and avogadros constant related?
1 mol= 6.02×10^23
What is a mole?
Mole is the amount of substance which contain the same number of particles as the number of atoms which are exactly there in 12g of C-12 isotope
Why do we need to balance chemical equations?
*They tell us how much of each substance is involved in a chemical reaction and how much product is made
- if we have too much of a reacting it will be wasted
*if we have too little of a reactant not all of the other reactant will react
- provides the molar ratios between the reactants and products
How to calculate the formula of a compound?
- the formula of a compound can be deduced using the masses of the reactants
- follow the law of conservation of mass
What is conservation of mass principle?
The total mass of a chemical reactions reactants is equal to the total mass of the product
What is molar ratio?
The ratio of the amounts (in moles) of each element in the reaction
What is the yield of a reaction?
Thee yield of a reaction is important when making a product in laboratory scale as well as in industrial scale
What are the reasons the mass of the reaction product can be less?
- Reversible reactions and the reaction is not complete
- Side reactions forming unnecessary by products
- Product may need to be purified so there will be loss of the products
What is theoretical yield?
This is calculated using the equation for the reaction assuming that the reaction goes into completion with no losses
What is actual yield?
It is the the actual mass obtained by weighing the obtained product and not by calculations
What is the formula for percentage yield?
(Actual yield÷theoretical yield) × 100
How is the stability of an industrial process assessed?
- Percentage yield
- Availability or scarcity of non-renewable materials
- The cost of raw materials
- The quantity of energy needed
What is atom economy?
The measure of efficiency since it measures the proportion of reactant atoms which are converted into the desired product.
Indicated the percentage of atoms from the starting materials that end up in the desired product
What is the formula for atom economy
(Mr of desired product ÷ total Mr of all products) ×100
