Empirical And Molecular Formulas Flashcards
What’s the empirical formula?
The smallest whole number ratio of atoms in a compand
What’s the molecular formula?
The actual number of atoms in a molecule
What’s the formula fer percentage composition of element x?
% Composition of x= total mass of element in compound/total mass of compound x100
What is water of crystallisation?
The water molecules incorporated into some compounds
What’s the opposite of hydrated compounds?
Anhydrous compounds
What steps do you need to follow to calculate the ratio of moles of anhydrous salt to moles of water?
- Number of moles of water lost (using mr mole)
- Number of moles of anhydrous salt
- Ratio in form 1:n
What 2 reasons could mean the actual yield is less than the theoretical?
Not all the starting chemicals have reacted fully/some chemicals are always ‘lost’ ( such as during transfers between containers)
What does the calculation table for calculating empirical formula look like?
The elements go across the top
Down the side:
- (%) mass
- Ar
- Mols
- ratio ( divide all mols values by the smallest)
Once you have the empirical formula, how do you calculate the molecular formula?
Find Mr of molec and divide it by Mr of empirical, then multiply the empirical by this value
What is the hydrated salts calculation table?
The same as empirical form, but with compounds across the top instead of elements
(mass, mr, mols, ratio- must be 1:n)