Empirical And Molecular Formulas Flashcards

1
Q

What’s the empirical formula?

A

The smallest whole number ratio of atoms in a compand

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2
Q

What’s the molecular formula?

A

The actual number of atoms in a molecule

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3
Q

What’s the formula fer percentage composition of element x?

A

% Composition of x= total mass of element in compound/total mass of compound x100

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4
Q

What is water of crystallisation?

A

The water molecules incorporated into some compounds

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5
Q

What’s the opposite of hydrated compounds?

A

Anhydrous compounds

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6
Q

What steps do you need to follow to calculate the ratio of moles of anhydrous salt to moles of water?

A
  1. Number of moles of water lost (using mr mole)
  2. Number of moles of anhydrous salt
  3. Ratio in form 1:n
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7
Q

What 2 reasons could mean the actual yield is less than the theoretical?

A

Not all the starting chemicals have reacted fully/some chemicals are always ‘lost’ ( such as during transfers between containers)

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8
Q

What does the calculation table for calculating empirical formula look like?

A

The elements go across the top
Down the side:
- (%) mass
- Ar
- Mols
- ratio ( divide all mols values by the smallest)

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9
Q

Once you have the empirical formula, how do you calculate the molecular formula?

A

Find Mr of molec and divide it by Mr of empirical, then multiply the empirical by this value

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10
Q

What is the hydrated salts calculation table?

A

The same as empirical form, but with compounds across the top instead of elements
(mass, mr, mols, ratio- must be 1:n)

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