(e) Table 1 shows the solubility of three solids in water at room temperature.
Table 1
Solid
The mass of the solid that
dissolves in 100 cm3 of
water
Phosphorus oxide
50 g
Silicon dioxide
og
Sodium hydroxide
100 g
A teacher labelled these three solids A, B and C.
She gave a student the information shown in Table 2
Table 2
Solid
Observation when added to water
pH of the solid in water
А
colourless solution
14
B
colourless solution
2
с
solid does not dissolve
7
Describe a method that could be used to identify each of the three solids A, B and C.
You must use an indicator in the method.
Use information in Table 1 and Table 2
(4)
(Total 9 marks)

first, consult an activity series chart to determine if al is more reactive than fe. it is, so it will replace the fe. now, one can continue with the problem.

next, make sure you have a correctly balanced equation.

3feo + 2al ==> 3fe + al2o3

now, determine which reactant (feo or al) is in limiting supply.

moles feo present = 125 g x 1 mole/71.8 g = 1.74 moles

moles al present = 25.0 g x 1 mole/26.98 g = 0.927 moles

since from the balanced equation, it take 3 mol feo for every 2 mol al, al will be limiting.

you can determine this simply by dividing moles of each by their coefficient in the balanced equation. for example: 1.74/3 = 0.58 and 0.927/2 = 0.464. al is less, so it is limiting.

finally, using the stoichiometry in the balanced eq. determine mass of fe that can be produced from 0.927 moles of al.

0.927 moles al x 3 moles fe/2 moles al x 55.8 g/mole = 77.6 g

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.