Question

What is the mass per repeating unit of PET (in g/mol)? explain why this number should be used ffor determning limiting reagent and yield and not the actual molecular weight of the polymer (which is >> 10,000 g/mol). I know that the mass per repeating unit of PET is 192 g/mol.

Answer 1

PET consists of polymerised units of the monomer ethylene terepthalate,with repeating units .C10H804.it is commonly recycled,and has the number,as its recycling symbol(.polyethylene terepthalate)

A repeat unit or repeating unit is a part of a polymer whose repetition would produce the complete polymer chain (except for the end-groups) by linking the repeat units together successively along the chain, like the beads of a necklace.

The theoratical yield for a reaction is calculated based on the limiting reagent.this allows the researchers to determine how much product can actually be formed based on the reagents present at begin of the reaction .

the actual yield must be 100% due to limitations.

% yield=(actual yield/theoretical yield)100

% yield measures how efficient the reaction is under certain conditions. The limiting reagent is always the substance with the lowest number of moles. The mass is NOT used to determine the limiting reagent. One way of finding the limiting reagent is by calculating the amount of product that can be formed by each reactant.

The limiting reagent or limiting reactant : in a chemical reaction is the substance which is totally consumed when the chemical reaction is complete. The amount of product formed is limitedby this reagent since the reaction cannot proceed further without it. If one or more other reagents are present in excess of the quantities required to react with the limiting reagent, they are called as excessreagents.