Question

You will have been given one of the molecules depicted in the introduction as your unknown (anthracene, naphtalene,fluorene, p-dichlorobenzene) Which do you believe it is? Base your choice on the experimental molar mass you calculated (123g/mol)from your data, and comment on how certain you are of your identification.

Answer 1

Hi, based on the molecules you mentioned in your question, we have the following molecular masses.

Anthracene = 178 g/mol

Naphthalene = 128 g/mol

Fluorene = 166 g/mol

p-dichlorobenzene = 147 g/mol

so, on the basis of these data, you molecule should be naphthalene since its molar mass is closest to your experimental molar mass 123 g/mol.

The difference between your experimental molar mass and naphthalene molar mass is 5 g/mol. Please note that a difference of 5 g/mol would make your experimental data questionable. Furthermore, I am unable to comment on the source of this error since you did not mention the method you used to obtain the experimental molar mass. Please note that different methods have different errors and molar mass determination of the same substance through different methods can give you different results. If you wish, you can post the experimental method in the comments and I would happily comment on possible sources of error and reliability of your measurements. I hope it helps.