Proving anthracene form.?

Question

you have 2.5 mg of anthracene in oxygen, causing 8.64 mg of CO2 and 1.2 mg of H20. HOW do you do this problem? I can do math, it would be more helpful to teach me the techniques necessary so I could answer further problems. I am very greatful for you help.

Answer 1

That's a combustion reaction!

1. Write first the balance equation:

2C14H10 (antracene) + 33O2 ----> 28CO2 + 10H2O

2. Determine the number of moles of 2.5mg of anthracene:

moles = g/MW of antracene
moles = 0.0025g/178g/mol = 1.4 x 10^-5 mol

3. Determine the weight of CO2 produced in 1.4 x 10^-5 mol of antracene:

Based from the balanced equation, ratio of #mol anthracene to #mol of CO2 is 2:28 or 1:14. Hence, number of moles of CO2 is

1.40 x 10^-5 mol x 14 = 1.97 x 10^-4 mol CO2

Get the weight: mol x MW of CO2

1.96 x 10^-4 mol x 44g/mol = 0.00865 g or 8.65mg of CO2

4. Do the same for water.

1 mol anthracene = 5 mole water
1.40 x 10^-5 mol x 5 = 7.0 x 10^-5 mol water
7.0 x 10^-5 mol x 18g/mol = 0.00126 g or 1.26mg of H2O