Quantitative Chemistry

Question 1

what is molar mass?

Answer 1

1 mole of a substance has a mass equal to its Ar or Mr in g

Question 2

what is the equasions to work out mass?

Answer 2

mass= num. of moles × Ar or Mr

Question 3

what is Ar and Mr?

Answer 3

Ar - relative atomic mass = the top number

Mr - relative formulary mass = the Ar of all the atoms in a compound.

Question 4

how do you work out % composition?

E.g. N in NH3

Answer 4

Ar (N) ×100
Mr (NH3)

Ar over Mr ×100

Question 5

how do you work out % yield?

Answer 5

actual mass( what was produced in the reaction) over theoretical mass( the mass calculated from molar ratio) ×100

Question 6

why is 100% yield not posible?

Answer 6

• impure reactants

- side reactions occur

Question 7

what is the molar gasses volume at room temperature?

Answer 7

1 mole of gass occupies 24 dm^3 (24 000 cm^3)

Question 8

what is Avigadro constant?

Answer 8

1 mole of a substance contains 6×10^23 particles

Question 9

steps to work out empirical formula?

do some test questions to learn this

Answer 9

1. list the element
2. write down the mass of each element
3. divide by the Ar of that particular element
4. divide by the smallest value
   (5. multiply to give while numbers)