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

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SUMMARY

The discussion focuses on determining the molecular formula of a hydrocarbon from a combustion analysis involving 6.0 cm³ of hydrocarbon and 34.5 cm³ of oxygen, resulting in 22.5 cm³ of gaseous products. The combustion reaction is represented as CxHy + (x + y/4) O2 → x CO2 + y/2 H2O. The calculated volumes indicate that 18 cm³ of CO2 and 4.5 cm³ of H2O are produced, leading to the conclusion that the hydrocarbon's molecular formula can be derived by converting these volumes to moles to find the values of 'x' and 'y'.

PREREQUISITES
  • Understanding of stoichiometry in chemical reactions
  • Knowledge of gas laws and volume relationships at room temperature
  • Familiarity with combustion reactions and products
  • Ability to convert gas volumes to moles using the ideal gas law
NEXT STEPS
  • Learn how to apply stoichiometric calculations in combustion analysis
  • Study the ideal gas law to convert gas volumes to moles
  • Explore the concept of limiting reagents in chemical reactions
  • Investigate the methods for determining empirical and molecular formulas from combustion data
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Chemistry students, educators, and anyone involved in analytical chemistry or combustion analysis will benefit from this discussion.

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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'.
 

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