Chemistry

posted by Natasha

In a laboratory activity, a student team measures the heat released by burning heptane. Using the following data, calculate the molar heat of combustion of heptane in kJ/mol:

Mass of water - 179.2 g
Initial water temperature - 11.6 degrees C
Final water temperature - 46.1 degrees C
Mass of heptane burned .585 g

Ok so the heat would be
(179.2)(34.5)(4.18) = 25842.43 J = 25.84 kJ, right?

And then the heat of combustion would be 25.84/44.17 = 44.17, right?

So what do I do after this? Is what I did even right?

  1. DrBob222

    25.84 kJ is correct but from there on no.
    44.17 looks like the molar mass of CO2 but I don't know why you need that (and it may be something else). You want kJ/mol HEPTANE (isn't that C7H16).
    25.84 kJ for 0.585 g sample so
    25.84 kJ/0.585 gives kJ/gram and that times molar mass heptane give kJ/mol heptane.

  2. Natasha

    Ok I messed it up when I wrote it, it should be 25.84/.585 = 44.17
    So then would it be
    44.17(100.23) = 4427.16 Is that right?

    The chart in my text says that the accepted molar mass of heptane is 4817. Is my answer too far away from the accepted value? Did I do it right?

  3. DrBob222

    It looks ok to me. I don't know what kind of accuracy you get in this type experiment but your error doesn't appear all that bad.
    %error = [(4817-4427)/4817]*100 = 8.1%

Respond to this Question

First Name

Your Answer

Similar Questions

  1. Urgent-Chemistry Help

    I need help with the heat effects and calorimetry worksheet. Please explain how to solve it! Thank you so much! A metal sample weighing 45.2g and at a temperature of 100.0 C was placed in 38.6g of water in a calorimeter at 25.6 C. …
  2. Chemistry

    when pure sodium hydroxide is dissolved in water , heat is evolved in a laboratory experiment measure a molar heat of solution of sodium hydroxide the following procedure was followed. to a calorimeter containing 300g of water at 20.0 …
  3. chemistry

    Can you check what I did below? On the first problem, I am not sure if I am suppose to add a negative to the first part of the heat loss of water like so -[C(sp)m(w)deltaT(w)]. On the second problem, part(a), I am not sure if I am
  4. chemistry

    While researching energy values of fuels, a chemist designed an experiment to find out the heat of combustion of pentane. Using the known hexane heat of combustion of hexane = 4650kJ/mol and the data below calculate the heat of combustion …
  5. chemistry

    While researching energy values of fuels, a chemist designed an experiment to find out the heat of combustion of pentane. Using the known hexane heat of combustion of hexane = 4650kJ/mol and the data below calculate the heat of combustion …
  6. Chemistry

    heptane and water do not mix, and heptane has a lower density (0.684g/mL) than water (1.00g/mL). A 100mL graduate cylinder with an inside diameter of 3.10 cm contains 39.90g of heptane and 34.00g of water. What is the combined height …
  7. chemistry

    If all the energy obtained from burning 1.23 pounds of propane (fuel value is 11.09 kcal/g) is used to heat 125.0 kg of water at an initial temperature of 21.8 °C, what is the final temperature?
  8. Molar heat of combustion question!

    Calculate the molar heat of combustion of paraffin, expressed in units of kJ/mol. First calculate the thermal energy released when one mole of parafin burns) because one mole of parafin (c25h52) has a mass of 325g, the molar heat of …
  9. chemistry

    Calculate the mass of ethanol that must be burnt to increase the temperature of 150g of water by 75 degrees celsius, if exactly 75% of the heat released by this combustion is lost to the surroundings. Also it is given that the heat …
  10. Chem

    A 2.461-g sample of glutamic acid, C5H9NO4 (147.13 g/mol) was burned in a bomb calorimeter with excess oxygen. The temperature of the calorimeter and the water before combustion was 23.76 °C; after combustion the calorimeter and the …

More Similar Questions