Chapter 3 - Amount of substance Flashcards
What is Avogadro’s constant?
6.02 x 10^23
What is molar mass?
The mass per mole of a substance, measured in g mol^-1
What is the equation for molar mass?
n (amount) = m (mass)/M (molar mass)
What is molecular formula?
The number of atoms of each element in a molecule
What is empirical formula?
The simplest whole-number ratio of atoms of each element in a compound
What is relative molecular mass?
Compares the mass of a molecule with the mass of an atom of carbon-12
What is relative formula mass?
Compares the mass of a formula unit with the mass of an atom of carbon-12
What is a hydrated salt?
A crystalline salt molecule that is loosely attached to a certain number of water molecules
What is water of crystallisation?
Water molecules that are bonded into a crystalline structure of a compound
What happens when hydrated salts are heated?
The bonds holding the water within the crystal are broken and the water is driven off, leaving behind a white powder anhydrous salt.
What is a standard solution?
A solution of known concentration
What is the equation for concentration?
Concentration = moles/volume
What is molar gas volume?
The volume per mole of gas molecules at a stated temperature and pressure
What is the equation for moles involving the molar gas volume?
Amount (mol) = volume/molar gas volume
What is the molar gas volume at RTP?
24dm^3
What is the ideal gas equation?
pV = nRT
What two assumptions does the ideal gas equation rely on?
The forces between molecules are negligible and the gas molcules have negilgible size compared to the size of their container
What is stochiometry?
The relationship between the relative quantities of substances taking part in a reaction or forming a compound, typically a ratio of whole integers.
Why is it unlikely a 100% yield is obtained?
Reaction may be reversible, purification of the product may result in loss of some product, initial reactants may not be pure, other side reactions may have taken place
Why is there a need for a high % yield?
To increase profits (wasting as little raw material as possible, maximise amount of product made from reactants)
What is the equation for % yield?
% yield = actual yield/theoretical yield x 100
What is a limiting reagent?
The reactant that is used up first, which limits the amount of product that can be formed
What is atom economy?
A measure of the amount of starting materials that end up as useful products
What is the equation for atom economy?
Atom economy = (total Mr of desired products/ total Mr of all products) x 100
