A 32.2 mg sample of the organic compound from problem 1 was treated to combustion analysis which yielded 59.2 mg CO2 and 12.3 mg of H2O. Analysis by low resolution mass spectrometry yielded a molar mass of 191 g/mol for the pure
compound. Further analysis showed that the compound contained only carbon, hydrogen, oxygen, and chlorine. What is the molecular formula of the compound?
I solved problem 1, which was "A 132.2 mg sample of a pure organic compound containing only chlorine as the halogen was treated in this manner. The
aqueous layer required 13.63 mL of 0.1015 M AgNO3 to reach the argentometric endpoint. What is the percentage chlorine by mass in the organic compound?" and got an answer of 37.1% Cl, which im pretty sure is right.
Here's what I did so far....
12.3mg H2O/18.01528mg x (1 O/1 H2O) = 0.6827mmol O
12.3mg H2O/18.01528mg x (2 H/ 1 H2O) = 1.3655mmol H
59.23mg CO2/44.0098mg x (1 C/1 CO2= 1.345mmol C
...divide them all by the lowest mole ratio= C2H2O
now i know there has to be a Cl in there somewhere, and there's also a stoicheometric ratio of 6 from (191mg/mmol)/(32.2mg)=6, bringing the formula to C12H12O6. this still doesn't have a Cl in it and its MW is already 252. I'm not sure if I'm supposed to factor in the O contribution from the CO2 as well, or how the Cl is factored into the equation and still getting a MW of 191...?© BrainMass Inc. brainmass.com October 17, 2018, 12:08 am ad1c9bdddf
What you know:
You have 32.2 mg of material
You have 37.2 % Cl
You have an overall molar mass of 191
You get 59.2 mg CO2 and 12.3 H2O from combustion
37.2% of 191 = 71 / 35.5 (mass of Cl) ...
Chemistry combustion sample calculations are examined in the solution.
Chemistry: Limiting Reagent and Enthalpy Sample Questions
I am having trouble setting up the follow problems. I am not even sure where to start. If anyone can offer any advice, I would greatly appreciate it, as I am completely stumped:
1) The volume in Liters of H2(g), measured at 22 degrees C and 745 mmHg, required to react with 30.0 L of CO (g), measured at 0 degrees C and 760 mmHg, in the reaction 3CO(g)+7H2(g) --> C3H8(g)+3H2O(l) is?
2) The complete combustion of propane, C3H8(g), is represented by the equation C3H8(g)+5O2(g)-->3CO2(g)+4H2O(l). Delta H (change of enthalpy)=-2220 kJ.
How much heat is involved in the complete combustion of 12.5L C3H8(g) at 25 degrees C and 790 mmHg?