chemical calculations Flashcards
1
Q
what is relative formula mass (Mr)
A
total atomic mass of all elements of a compound
- H2O (h=1) (2h=2) (o=16) (2h+o=18)
2
Q
what are moles (mols)
A
the amount of substance in the relative atomic or formula mass of a substance in grams
3
Q
relative formula mass formula
A
mass = mols x Mr
4
Q
what is the limiting reactant
A
the reactant that is used up first in a reaction
5
Q
what is the concentration of a solution
A
the amount of a substance dissolved in 1dm^3 of a solution
6
Q
concentration formula (titration)
A
concentration = mols (g) / volume (dm^3)
7
Q
what is titration
A
a method for measuring the volumes of 2 solutions that react together
8
Q
titration method
A
- measure acid or base using glass pipette and pour into conical flask
- add 2-3 drops of phenolphthalein indicator to flask
- fix burette to stand and fill with other liquid until the meniscus is at 0
- open tap and let drops fall slowly, continuously stirring flask
- when solution changes colour, turn off tap and record burette reading
- repeat for accurate/ reliable results
9
Q
volumes of gases
A
the volume of 1 mole of any gas at room temp is 24dm^3
10
Q
number of moles in a gas formula
A
mols = volume / 24
