[satycorn]

Hi everyone!

A test is near and I have some difficulties with some problems in organic chemistry, I would sincerely appreciate any help. Most of them consist of finding the organic compound (mostly Alkenes, alkanes, alkines, alkynes and benzene), my troubles are when the relative density compared to air is given and you need to find the compound, or when the reaction is given and the mass of the products, and from there you have to find the original organic compound.

1) From burning 7,2 litres of an alkyne, we get 26,4 grams of carbon dyoxide CO2 and 5,4 grams of H2O. Determine the formula of the alkyne.

2) 700grams of CaC2 react with water H2O and give 120litres of C2H2. Find the mass in grams of benzene C6H6? (I understand that it has to do with polymerization of C2H2, but how do I use the fact that I have 700grams of CaC2 reacting with water?

3) A mixture of ethane+ethene+ethyne is burned in the presence of O2 from air.

a) How many litres of Oxygen is needed for burning 10 litres of the mixture?

b) In how many litres of air is found this amount of oxygen?

4) Benzene reacts with chlorine in presence of FeCl3. Chlorine is 31.5% of the mass of the produced compound.

a) Determine the molecular formula of the compound that is produced.

b) Determine it's molecular mass.

c) Determine the type of the reaction.

These are some of the problems, I'd really appreciate any help.

Thank you.

[Dan]

As you have already been told before: You must show that you have attempted the question. This is a Forum Rule.

Start with balanced chemical equations.

[satycorn]

As you have already been told before: You must show that you have attempted the question. This is a Forum Rule.

Start with balanced chemical equations.

I am sorry. Here are my attempts for each problem:

1)x litres of Alkyne→n x 44grams of CO2
7,2 litres→26,4

But, what do I do with the water?? How do I find the "n"?

2)  I understand that a molecule of benzene is produced by polymerizing 3 molecules of ethyne (C2H2), but how in the world do I use the given info, when I know both the amount of CaC2 that reacts with water and the volume of C2H2 that I get from the reaction? What do I need to estimate??

3)  C2H6+C2H4+C2H2+O2=CO2+H2O
This is the difficult part, I am not sure whether I have done the equation above correctly or not?? Do I need to take each compound (ethane, ethene and ethyne) and do their burning reactions separately? What do I do from there?

Thank you.

I am really stuck with the fourth one