Metal Displacement Reactions Count the number of different metal ions that react

ID: 1057762 • Letter: M

Question

Metal Displacement Reactions Count the number of different metal ions that reacted with each metal sheet Metal sheet Number of Reacting lons Copper (Cu) Lead (Pb) Tin (Sn) Zinc (Zn) Based on the metal displacement data (not necessarily following Fig. 1), list the six metals. copper, iron, lead, magnesium, silver, and tin, in the order of most active to least active. Least Active Most Active Combine the analyses of the H2 and metal displacement reactions to list all eight metals investigated in the order of most active to least active. is conclusion must follow from the experimental results and not necessarily from Fig. 1) Least Active Most Active

Explanation / Answer

V. Refer to the chart in V. (Metal displacement reactions) and answer this one:

Metal sheet

Number of reacting ions

Copper (Cu)

1 (only Ag+)

Lead (Pb)

2 (Cu2+, Ag+)

Tin (Sn)

0 (None of the ions reacted)

Zinc (Zn)

3 (Zn2+ can displace Ag+ from its salt; you possibly didn’t observe the reaction; so Cu2+, Fe3+ and Ag+ reacts.

Now lets find out how many ions reacted with these metals:

Cu2+ (1, only Pb sheet), Fe3+ (1, only Zn sheet), Pb2+ (0, none), Mg2+ (0, none), Ag+ (2) and Sn2+ (0, none).

The metals which show no reaction indicates that they are more reducing and lack of a reaction means that these metals can only reduce the less reactive metal ions to their elemental form. Therefore, the decreasing order of reactivity is

Mg2+ > Fe3+ > Sn2+ > Pb2+ > Cu2+ > Ag+

The most active is Mg2+and the least active is Ag+.

Hydrogen displacement reactios:

The most active metal is the one which can displace hydrogen from cold water while the least active metal cannot displace hydrogen from hot acid. Note the observations:

a) Ca displaces hydrogen from cold water – most active.

b) Copper cannot displace hydrogen from water or acids (says very slow reaction with hot acid) which essentially means no reaction.

c) Fe displaces hydrogen from hot acid and slowly from hot water – intermediate reactivity.

d) Pb can actually displace hydrogen from hot acid (the reaction can be slow but it occurs).

e) Mg can displace hydrogen from hot water and acids – hence high reactivity.

f) Sn displaces hydrogen from hot acid (shouldn’t displace hydrogen from water; atleast hydrogen isn’t eveolved, tin hydroxide forms).

g) Zn displaces hydrogen from acid.

Therefore, the reactivity order is

Ca > Mg > Fe > Zn > Sn Pb > Cu

The most active is Ca while Cu is the least active.