Topic 7 - Calculations

Question 1

empirical formula

Answer 1

• simplest whole number ratio
• of atoms of each element within that compound

Question 2

conservation of mass

Answer 2

no mass is lost or gained during a chemical reaction.
same atoms just arranged different way

Question 3

closed system

Answer 3

the total mass of the system before or after stays the same
- precipitation reactions

Question 4

reactions where mass seems to increase

Answer 4

• the container isn’t sealed
• at least one of the reactants are g and all of the products are s , l or aq
• this is because the reactant gas is not contained in the vessel so you can’t account for its mass
• the particles of the product are all contained

Question 5

reactions where mass seems to decrease

Answer 5

• the container isn’t sealed
• all the reactants are s , l or aq and at least one of the products are g
• the gas that’s produced can escape and is no longer contained

Question 6

concentration

Answer 6

mass ( g) / volume (dm3)

Question 7

how to convert cm3 into dm3

Answer 7

divide by 1000

Question 8

limiting reactant

Answer 8

the reactant that gets used up and causes the reaction to stop

Question 9

product and limiting reactant correlation

Answer 9

the amount of product formed is directly proportional to amount of limiting reactant used

Question 10

Avogadro constant

Answer 10

6.02 x 10^23

Question 11

what is a mole

Answer 11

one mole of any substance contains an Avogadro number of particles

Question 12

mole equation

Answer 12

mass = Mr x moles