Formula and amounts (MOLE)

Question 1

What are amounts of substances measured in

Answer 1

Moles (mol)

Question 2

Give the number of particles on one mole of a substance

Answer 2

6.02 x 10^23 particles - this is called avagadros constant

Question 3

What is the molar mass of a substance

Answer 3

The molar mass is the mass per mole of a substance in g mol^-1

Question 4

How do you work out the molar mass of a substance

Answer 4

Add up the relative atomic masses of all the elements in the molecule
eg: CaCO3 - 40.1 + 12 + 16 + 16 + 16 = 100.1

Question 5

Give the formula to work out the number/ amount of moles in a substance

Answer 5

moles (mol) = mass (g) / molar mass (g mol^-1)

Question 6

How would you work out the number of particles or atoms in a substance from the number of moles it has

Answer 6

Moles ( mol) x avagadros constant

Question 7

Give the equation to work out the concentration of a substance using the number of moles it has

Answer 7

concentration ( mol dm^-3 ) = moles (mol) / volume (dm^3)

Question 8

Give the equation to work out the concentration of a substance using its mass

Answer 8

concentration ( g dm^-3 ) = mass (g) / volume (dm^3)

Question 9

What is the molecular formula

Answer 9

The actual number of atoms of different of different elements within a compound

Question 9

What is the empirical formula

Answer 9

The simplest whole number ratio of the atoms of different elements within a compound

Question 10

Describe how to work out the empirical formula of a compound from experimental results and from percentages

Answer 10

1) Write out the mass of each element
2) Write down molecular mass (Mr) of each element
3) From the information above work out the number of moles using mass/ Mr
4) Divide all the numbers by the smallest number of moles
5) This will have produced a ratio of each element in the compound