TOPIC C3 QUANTITATIVE CHEMISTRY

Question 1

what is relative formula mass

Answer 1

-MR
relative atomic mass of all atoms in the molecular fomrula added together
e..g MGCL2
Ar of MG= 24 and Ar of Cl=35.5

Question 2

percentage mass of an element in a compound formula

Answer 2

Ar x number of atoms of that element divided by Mr of the compound
x100

Question 3

formula to find the number of moles

Answer 3

mass in g (of an element or compound)
DIVIDED BY
Mr (of the element or compound)

Question 4

what does conservation of mass mean

Answer 4

mass can not be created or destroyed

Question 5

explain why in an experiment, you may observe a change of mass of an unsealed reaction vessel

Answer 5

-if mass increases, it is because one of the reactants is a gas, found in air
-before the reaction, gas floats around in the air and if its not contained in the reaction vessel , you cant account for its mass

Question 6

the mole and equations

Question 7

when do reactants stop

Answer 7

when 1 reactant is used up
-the reacted that is used up is named the limiting reactant

Question 8

how to calculate mass of product formed with in a reaction

Answer 8

-by using the mass of the limiting reactant and the balanced reaction equation
1. write out balanced equation
2. work out relative formula masses
3. how many moles there are in the substance
4. use equation to work out how many moles the’ll be

Question 9

what is concentration

Answer 9

the amount of a substance in a certain volume of a solution

Question 10

the more solute…

Answer 10

the more concentrated the solution

Question 12

what is concentration measured in

Answer 12

g/dm3

Question 13

how to calculate concentration

Answer 13

mass of solute in g
DIVIDED BY
volume of solvent in dm3