quantitative chemistry Flashcards
define relative atomic mass
the mass of an atom compared to the mass of carbon-12 which has a mass of exactly 12
% of an element in a compound= ?
mass of element in compound/relative formula mass x 100
percentage yield=
actual yield/theoretical yield x 100
state 3 reasins why it is impossible to obtain a 100% yield
- the reaction may not have gone to completion
- there may have been loss of productas as it was transferred during filtration etc.
- some of the reactants may have reacted to form different products
define water of crystallisation
water that is chemically bonded into the crystal structure
what is it meant by the term hydrated
a substance contains water of crystallisation
what is meant by the term anhydrous
a substance has lost water of crystallisation
what is ‘heat to a constant mass’
weigh sample, heat and reweigh. keep doing this until the mass does not change
what is thermal decomposition
breaking down a substance using heat
suggest a reason for the water of crystallisation to be lower than expected
the salt has not been heated to a constant mass
suggest a reason for the water of crystallisation to be higher than expected
the salt may have decomposed when heated
what is empirical formula
the simpilist whole number ratio of atoms in a molecule
what is molecular formula
the actual number of atoms in a molecule
moles equation
moles = mass/mr
