1.e - Chemical formulae, equations and calculations

Question 1

now state symbols and be able yo balance equations

Answer 1

solid = s
liquid = l
gas = g
aqueous = aq

Question 2

how do your work out Mr ( relative formula mass) from At ( relative atomic masses )

Answer 2

Mr ( compound ) = all the Ar s of the atoms it contains added together

Question 3

definition of mole ( mol )

Answer 3

unit for the amount of a substance

one mole of atoms / molecules of any substance will have a mass in grams equal to the Ar/ Mr for that substance

Question 4

what is rhyme for mass, Mr , moles and equation

Answer 4

Massive Mr Mole

- mass = Mr x moles

Question 5

how to calculate reacting masses ( theoretical yields )

Answer 5

??? pg. 26

1. Write out balanced equation
2. work out Mr
3. calculate no. of moles
4. look at ratio of moles
5. calculate mass ( mass = Mr x moles )

Question 6

how to calculate % yield

Answer 6

% yield = actual yield (grams) / theoretical yield (grams ) x 100

( theoretical yield can be calculated from balanced equation and reacting masses )

Question 7

definition of empirical formula

Answer 7

simplest formula that tells you a ratio of different elements of a compound

Question 8

definition of molecular formula

Answer 8

tells you the actual number of atoms of each element in a single molecule

molecular formulas are whole number multiples of empirical formula

Question 9

how to calculate empirical formula

Answer 9

1. list all elements in a compound
2. write empirical mass ( if % write % )
3. Find no. of moles of each element
4. divide by smallest no. of moles
5. Get ration in simplest whole no. form ( divide / x / leave )

Question 10

how to calculate molecular formula

Answer 10

1. find Mr of empirical formula
2. molecular mass / empirical mass
3. multiply each element in empirical formula by answer to no. 2