Out of Fe,Cu,Sn and Hg, the most reactive metal
is ____and least reactive metal is_____.

Explanation

To determine the most and least reactive metals among Fe (iron), Cu (copper), Sn (tin), and Hg (mercury), we can refer to the reactivity series of metals. The reactivity series ranks metals based on their ability to displace other metals from their compounds and their tendency to oxidize.

### Step-by-Step Solution:

1. **Understanding Reactivity Series**:
The reactivity series is a list of metals arranged in order of decreasing reactivity. The higher a metal is in the series, the more reactive it is.

2. **Identifying the Metals**:
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