Why is the formula for polyethylene somtmes written C2H4n?

Answer 1

because the n on the end signifies that the C2H4 (ethylene) molecules have been linked an unspecified number of times (poly) to form a chain polymer.

It's called polymerisation and in this case to produce polyethylene, better known as polythene

Answer 2

The formula C2H4n is used to represent polyethylene, a polymer made up of repeating units of ethylene (C2H4). The letter 'n' represents the number of repeating units (monomers) in the polymer chain, which can vary in length. This notation simplifies the representation of a large and variable number of monomer units in the polymer structure.