1.3 Calculations

Question 1

Relative isotopic mass =

Answer 1

mass of 1/12 atom of 12C

Question 2

Relative atominc mass of an element
(Ar)

Answer 2

(Rel.isotopic mas of A x Rel abundance of isotope A) + (Rel.isotopic mas of B x Rel abundance of isotope B)

Question 3

Relative molecular mas
(Mr)

Answer 3

mass of 1/12 atom of 12C

Question 4

Calculating empirical formula

Answer 4

Creu tabl

Ratio by mas
Ratio by moles
Whole number ratio

Question 5

number of moles (n) =(amount of substance)

Answer 5

n =mas (g)/ Mr (gmol-1)
n= concentration x volume

Question 6

Number of particles (N) =

Answer 6

N=nxL

N= number of moles x Avogadro’s constant

Question 7

How to change cm3 into dm3?

Answer 7

divide by 1000

Question 8

25 degrees Celsius is how many Kelvin?

Answer 8

298K

Question 9

0 degrees Celsius is how many Kelvin?

Answer 9

273K

Question 10

How to work out moles in solutions?

Answer 10

n = v x c

Question 11

% yield of a reaction =

Answer 11

actual mass/ theoretical mass x 100

Question 12

atom economy =

Answer 12

mass of required products/ total mass of reactants x 100

Question 13

The ideal gas equation

Answer 13

PV = nRT

Question 14

% of error

Answer 14

max error/ volume of measurement x 100

Question 15

Maximum % error of burette

Answer 15

+- 0.05cm3 per reading
+- 0.1 per titration (you read the burette twice)

Question 16

Maximum % error of pipette

Answer 16

25cm3 pipette has a max error of 0.06cm3

Question 17

Maximum % error of a 2 decimal point balance

Answer 17

0.005g

Question 18

Maximum % error of a 3 decimal point balance

Answer 18

0.0005g