Calculations

Question 1

what is a mole

Answer 1

unit amount of substance that contains 6.02x10^23 particles

Question 2

link between 1 mole and relative formula mass

Answer 2

1 mole = relative formula mass expressed in grams

Question 3

what is the avogadro constant

Answer 3

6.02x10^23

Question 4

equation to find no. of moles

Answer 4

No. of moles = mass/Mr

Question 5

Process for reacting mass calculations

Answer 5

1) Find no. of moles of reactant with given mass
2) use molar ratio to find number of moles of unknown mass reactant
3) use no. of moles and Mr of unknown mass reactant to find mass

no. of moles = mass/Mr

Question 6

what are the 2 concentration calculations (to find conc per grams/moles)

Answer 6

conc = mass of solute (grams) / vol of solution (dm^3)

conc = moles of solute / vol of solution in dm^3

Question 7

what is empirical formula

Answer 7

simplest whole number ratio of of atoms/ions of each element in a compound

Question 8

what is molecular formula

Answer 8

actual number of atoms of each element in 1 molecule of a substance (either same as empirical formula or an exact multiple)

Question 9

What is Mr

Answer 9

Relative Formula Mass:
- sum of relative atomic masses of all atoms/ions in its chemical formula

Question 10

How do you calculate empirical formula (given mass of elements)

Answer 10

1) divide given mass of each element by Ar
2) divide both answers by the smaller number
3) Find simplest whole number ratio (either round or multiply)

Question 11

How do you determine a molecular formula from an empirical formula and the relative formula mass

Answer 11

1) Work out relative mass of the empirical formula
2) Divide Mr by relative empirical formula mass
3) multiply empirical formula by answer to determine molecular formula