Chemistry What Is the Molecular Formula of the Hydrocarbon in This Combustion Analysis?

AI Thread Summary
The discussion focuses on determining the molecular formula of a hydrocarbon from combustion analysis data. A gaseous hydrocarbon reacted with oxygen, producing carbon dioxide and water, with specific volumes measured before and after the reaction. The initial equation proposed for the combustion reaction is evaluated for correctness, and the volumes of carbon dioxide and water produced are calculated. Participants suggest converting the volumes of carbon dioxide and water to moles to find the values of 'x' and 'y' in the hydrocarbon formula. The conversation emphasizes the need to accurately account for the volumes of reactants and products to derive the molecular formula.
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Homework Statement




6.0 cm^3 of a gaseous hydrocarbon was sparked with 34.5 cm^3 of oxygen. The volume of the gaseous products after cooling to room temperature was 22.5 cm^3. The volume was reduced to 4.5 cm^3 on passing the gases through aqueous potassium hydroxide. What is the molecular formula of hydrocarbon?

Homework Equations





The Attempt at a Solution



CxHy + ( x + y/4 ) O2 ----> x CO2 + Y/2 H2O

Is this equation correct?Do I miss out any product?

my doubts : First, I try calculating the volume of CO2 produced and It is 18cm^3 and the volume of H2O is apparently 4.5 cm^3. What should I do next?
How to find the volume of oxygen gas that has reacted? Should I convert them into moles by dividing the volume of room temperature? I'm confused :(
 
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Ose90 said:
First, I try calculating the volume of CO2 produced and It is 18 cm3 and the volume of H2O is apparently 4.5 cm3. What should I do next?
How to find the volume of oxygen gas that has reacted? Should I convert them into moles by dividing the volume of room temperature? I'm confused :(


You have found the volume of CO2. Convert it to moles to determine 'x'. What remains is water vapor. Find the number of moles of that and determine 'y'.
 
Thread 'Confusion regarding a chemical kinetics problem'

Thread 'Confusion regarding a chemical kinetics problem'

TL;DR Summary: cannot find out error in solution proposed. [![question with rate laws][1]][1] Now the rate law for the reaction (i.e reaction rate) can be written as: $$ R= k[N_2O_5] $$ my main question is, WHAT is this reaction equal to? what I mean here is, whether $$k[N_2O_5]= -d[N_2O_5]/dt$$ or is it $$k[N_2O_5]= -1/2 \frac{d}{dt} [N_2O_5] $$ ? The latter seems to be more apt, as the reaction rate must be -1/2 (disappearance rate of N2O5), which adheres to the stoichiometry of the...
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