3. If x electrons are needed to displace 108 g silver from a solution which contains Ag ions, how many electrons are needed to displace 9 g of aluminium from a solution which contains
Al ions?

[Relative atomic mass Al, 27; Ag, 108]
A X
B 3x
C 4x
D 9x

Choice A. electrons would be required for displacing of aluminum from a solution of ions.

Assumption: by " ions" the question meant with a charge of on each ion.

Explanation:

The question states that the relative atomic mass of is . In other words, each mole of

Therefore, that of silver that were formed would contain of silver atoms.

Metallic silver would precipitate out of this solution only after these ions are turned into atoms.

One ion carries one unit of positive electrical charge. On the other hand, each   carries one unit of negative electrical charge.

Therefore, each ion will need to gain one electron to form a neutral atom.

.

At least   of electrons would be required to turn of ions into that of silver atoms (which have a mass of .)

Hence, .

Unlike ions, each aluminum ion carries three units of positive electrical charge. That is three times the amount of charge on one ion. Therefore, three electrons will be required to turn one ion to an atom.

The question states that the relative atomic mass of is . Therefore, each mole of atoms would have a mass . There would be of atoms in that of .

It takes of electrons to turn one mole of ions to one mole of atoms. Hence, of electrons would be required to produce that of atoms (which has a mass of ) from ions.

That corresponds to the first choice, electrons.