chemistry

posted by .

Combustion analysis, Empirical and Molecular formulas, help!?


When 2.686 grams of a hydrocarbon, CxHy, were burned in a combustion analysis apparatus, 9.224 grams of CO2 and 1.511 grams of H2O were produced.

In a separate experiment, the molar mass of the compound was found to be 128.2 g/mol. Determine the empirical formula and the molecular formula of the hydrocarbon.

Enter the elements in the order presented in the qustion.

  • chemistry -

    empirical formula is the smallest whole number ratio

    molecular formula is the empirical doubled i believe.

  • chemistry -

    you would divide the grams of each molecule produced by the smallest ratio to find the subscripts.

  • chemistry -

    Start from a balanced equation

    CxHy + (x+y/4)O2 -> xCO2 + y/2 H2O

    so 1 mole of CxHy (molar mass 12x+y)produces
    x mole of CO2 and
    y/2 mole of H2O

    so
    2.686 g/(12x+y) moles

    produces
    9.224/44 =x moles of CO2
    so x=0.2096

    and produces

    1.511/18=y/2 moles of H2O
    so y=0.1679

    so the ratio is
    x:y
    0.2096:0.1679
    or 5:4

    Thus the empirical formula or the simplest formula is
    C5H4
    for which molar mass is 64 g

    we are told in the question that the molar mass is 128.2 g so the molecular formula (ie. the formula for one mole) must be C10H8, that is twice the empirical formula in this case.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. chemistry

    a flask with a volume of 267.5 mL contains a few milliliters of a volatile hydrocarbon. after vaporizing the gas at 100 degrees C, the flask is weighed and found to contain 0.728 grams of hydrocarbon vapor at 755 mmHg. a separate combustion …
  2. Chemisty!

    a flask with a volume of 267.5 mL contains a few milliliters of a volatile hydrocarbon. after vaporizing the gas at 100 degrees C, the flask is weighed and found to contain 0.728 grams of hydrocarbon vapor at 755 mmHg. a separate combustion …
  3. Chemistry

    When 1 gram of sex hormone (contains C, H, and O) was burned in a combustion analysis, 1.5 grams of CO2 and 0.405 grams of H2O were obtained. The molar mass was found to be 352g/mol. What is the molecular formula for the sex hormone?
  4. chem

    when hydrocarbons are burned in a limited amount of air CO as well as CO2 form. When 0.450 grams of a particular hydrocarbon was burned in air, 0.467 grams of CO, 0.733 grams of CO2, and 0.450 grams of H20 were formed. a. What is the …
  5. Chemistry

    2) What is the empirical formula of a compound containing C, H, O if combustion of 1.23g of the compound yields 1.8g CO2 and .74g of H2O 3) What are the empirical and molecular formulas of a hydrocarbon if combustion of 2.10g of the …
  6. chem 1411

    A combustion analysis of a 0.00134g sample (CxHy) of a hydrocarbon yields 0.00375g of CO2 and 0.00164g of H2O. What is the empirical formula of the hydrocarbon?
  7. Science

    10. ALTERNATIVE B The elementary analysis of 22 g hydrocarbon sample results in 18 g C and 4 g H. a) Choose the correct chemical formula of the hydrocarbon: i) CH4 ii) C2H4 iii) C3H8 b) What is the amount of CO2 in grams formed by …
  8. Science Chemistry

    The elementary analysis of 22 g hydrocarbon sample results in 18 g C and 4 g H. a) Choose the correct chemical formula of the hydrocarbon: i) CH4 ii) C2H4 iii) C3H8 b) What is the amount of CO2 in grams formed by the total combustion …
  9. chem

    When 3.517 grams of a hydrocarbon, CxHy, were burned in a combustion analysis apparatus, 11.59 grams of CO2 and 3.164 grams of H2O were produced. In a separate experiment, the molar mass of the compound was found to be 40.06 g/mol. …
  10. chemistry

    A 8.408 gram sample of an organic compound containing C, H and O is analyzed by combustion analysis and 12.53 grams of CO2 and 3.849 grams of H2O are produced. In a separate experiment, the molar mass is found to be 118.1 g/mol. Determine …

More Similar Questions