Amount of substance Flashcards
What is amount of substance?
The name given to counting the number of particles in a substance - the unit is the mole
What is the mole?
The unit for amount of substance. The amount of substance that conatins 6.02 x 10^23 particles
What is Avogadro’s constant?
The number of particles in 1 mole of carbon-12
Na = 6.02 x 10^23
What is molar mass?
The mass per mole of a substance
What is the moles and molar mass equation?
n = m/ Mr
n = moles
m = mass g
Mr = molar mass gmol^-1
What is molar gas volume?
The volume occupied by one mole of any gas at RTP. It has a value of 24 dm^3
What is empirical formula?
The simplest whole number ratio of atoms of each element present in a compound
What is molecular formula?
The number and type of atoms of each element in a molecule
What is water of crystallisation?
Water molecules that form part of the crystalline structure of a compound
What does does anhydrous mean?
A crystalline compound containing no water
What does hydrated mean?
A crystalline compound that contains water
What is the procedure to find the formula of a hydrated salt?
What are the assumptions made when finding the formula of a hydrated salt?
- All of the water has been lost
- No further decomposition occurs
What is the molar gas volume?
n = V/ 24
in dm^3 at RTP
What is the moles, concentration and volume equation?
n =cv
n = moles mol
c = concentration mol dm^-3
v = volume dm^3
What is the ideal gas equation?
pV = nRT
p = pressure Pa
V = volume m^3
n = moles mol
R = ideal gas constant = 8.314
T = temperature K
What is stoichiometry?
The ratio of amount of substance of each substance in mol
What is theoretical yield?
The maximum possible amount of product
What is the equation for percentage yield?
Percentage yield = (actual yield / theoretical yield) x100%
Why is theoretical yield difficult to reach?
- The reaction may not have gone to completion
- Side reactions may have taken place alongside the main reaction
- Purification of the product may results in loss of product
What is the limiting reagent?
The reactant that is not in excess - has the most mole in stoichemoetry
What is atom economy?
A measure of how well atoms have been utilised
What is the equation for atom economy?
Atom economy = (sum of Mr’s of desired products / sum of Mr’s of all products) x 100
How do you find a relative molecular mass experimentally using pV = nRT?
How can you experimentally identify and unknown metal?
The higher the atom economy of a reactant, the _____ sustainable it is
More
Less energy and reactants are required to form more products. Despite this, reactions with a high atom economy may have a poor percentage yield; efficiency is dependant on both of these factors
