chemical calculations

Question 1

what is relative formula mass (Mr)

Answer 1

total atomic mass of all elements of a compound
- H2O (h=1) (2h=2) (o=16) (2h+o=18)

Question 2

what are moles (mols)

Answer 2

the amount of substance in the relative atomic or formula mass of a substance in grams

Question 3

relative formula mass formula

Answer 3

mass = mols x Mr

Question 4

what is the limiting reactant

Answer 4

the reactant that is used up first in a reaction

Question 5

what is the concentration of a solution

Answer 5

the amount of a substance dissolved in 1dm^3 of a solution

Question 6

concentration formula (titration)

Answer 6

concentration = mols (g) / volume (dm^3)

Question 7

what is titration

Answer 7

a method for measuring the volumes of 2 solutions that react together

Question 8

titration method

Answer 8

1. measure acid or base using glass pipette and pour into conical flask
2. add 2-3 drops of phenolphthalein indicator to flask
3. fix burette to stand and fill with other liquid until the meniscus is at 0
4. open tap and let drops fall slowly, continuously stirring flask
5. when solution changes colour, turn off tap and record burette reading
6. repeat for accurate/ reliable results

Question 9

volumes of gases

Answer 9

the volume of 1 mole of any gas at room temp is 24dm^3

Question 10

number of moles in a gas formula

Answer 10

mols = volume / 24