Which reaction will occur?
2nabr + i2 mc023-1.jpg 2nai + br2
2fe + al2o3 mc023-2.jpg 2al + fe2o3
2agno3 + ni mc023-3.jpg ni(no3)2 + 2ag
pb + zn(c2h3o2)2 mc023-4.jpg zn + pb(c2h3o2)2

A single replacement reaction is one in which a more reactive element displaces a less reactive element from its salt solution.

1)

As iodine is less reactive than bromine, it will not be able to displace bromine from its salt solution, hence no reaction will occur.

2)

As iron lies lower in reactivity series, it is less reactive than Aluminium. It will not be able to displace aluminium from its salt and hence no reaction occur.

3)

As nickel lies above in reactivity series, it is more reactive than silver. It will be able to displace silver from its salt and hence reaction will occur.

4)

As lead lies lower in reactivity series, it is less reactive than zinc. It will not be able to displace zinc from its salt and hence no reaction occur.