Quantative Chemistry Flashcards Preview

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Flashcards in Quantative Chemistry Deck (11):
1

What is the formula for the amount of moles a substance has?

Amount (mol) = mass / mr

2

How do you work out the mass of an element in a compound?

%of Element in Ar of element in compound
the compound = _________________________________ X 100
Mr of the compound

3

What is the empirical formula?

Simplest whole number ratio o Fatima of each element

4

What is the molecular formula?

Shows all of the atoms of each element grouped together

5

How do you work out the empirical formula of a compound?

1. For each element you divide the mass by the Ar, to get the amount in moles
2. You then divide them all by the smallest
3. Then you have the simplest ratio

6

How do you convert empirical formula into molecular formula?

1. Work out the empirical formula mass
2. Divide the relative formula mass by the empirical mass
3. Multiply the empirical formula by the answer to part 2

7

How do you work out a reacting mass calculation?

1. Work out the amount in moles of the substance you are given the information for
2. Work out the amount in moles of the other substance using the equation
3. Work out the mass of the other substance

8

E.g What mass of Iron is produced when 32kg of iron oxide is heated with CO?
Fe2O3 + 3 CO -> 2 Fe + 3 CO2

1. Amount of Iron Oxide = 32000/160 = 200
2. 1 mole of iron oxide is equal to 2 moles of iron. Therefore amount in moles of iron = 400 mol
3. Mass of iron = 400 X 56 = 22,400g

9

How much does 1 mole of gas occupy?

24,000 cm3 or 24 dm3

10

How do you work out the volume of a substance?

1. Work out the amount in moles of the substance you are given the information for
2. Work out the amount in moles of the other substance using the equation
3. Work out the volume of the other substance

11

E.g What volume of oxygen is required for the complete combustion of 11.5 g of sodium?

4 Na + O2 ---> 2 Na2O

1. Moles of Na = 11.5/23 = 0.5
2. Moles of O2 = 0.5/4 = 0.125
3. Volume of O2 = 0.125 X 24 = 3 dm3