moles

Question 1

how much is one mole worth

Answer 1

6.02 x 10 to the 23

Question 2

equation to calculate moles

Answer 2

moles = mass/RFM

Question 3

how to workout the % composition of an element in a compound

Answer 3

ram of element / rfm of compound

Question 4

what is the % of C in CaCO3

Answer 4

RFM of CaCO3 = 100
RAM of C = 12
% = 12

Question 5

what is empirical formula

Answer 5

lowest possible whole number ratio of formula

Question 6

calculate empirical formula of compound x which contains 50% of O and 50% of S

Answer 6

S      O
50    50
32    32               EF is SO2
1.56   3.125 
1         2

Question 7

compound B contains 47.35% C, 10.6% H and 42.05 O

it has an RFM of 228 calculate the molecular formula

Answer 7

empirical formula = C3H8O2
12 x 3 + 1 x 8 + 2 x 16 = 76
228/76= 3
MF= C9H2406

Question 8

finding x - 2.495g of CuSO4.xH2O is heated and the mass decreases to 1.595

Answer 8

mass of CuSO4 = 1.595
mass of H2O = 0.9 
CuSO4        H2O
1.595            0.9
159.5            18
0.01               0.05
1                      5                  x=5

Question 9

how to calculate the limiting reagent

Answer 9

• write out equation
• pick one of the reactants
• calculate the moles with equation
• find the moles of the other reactant
• find mass
• have you got enough
  
  • yes 1st reactant is limiting
  • no 2nd reactant is limiting

Question 10

calculating limiting regent example

30g of Li2O with 36.5g of HCl which is the limiting regent

Answer 10

Li2O + 2HCl —-> 2Li2O + HCl
15 36.5
30 36.5 Li2O is limiting
0.5 1

Question 11

equation for calculating % yield

Answer 11

actual yield/ theoretical yield x 100