posted by .

Can one calculate the number of moles of air? If so, calculate the number of moles in 1 kg of air (making sure your calculation, units and assumptions are fully explained); If not, explain why it is not possible to calculate the number of moles of air.

  • chemistry -

    Air is a mixture of several gases. But the most abundant is Nitrogen and Oxygen. Their mole percent in air is:
    N2 = 78%
    O2 = 21%
    Ar = 1%
    *Actually the 1% here is not entirely Argon, but Argon is the most abundant in that 1%.
    Note that these values are NOT EXACT, but is just an estimation. To calculate for number of moles of air given the mass of air, determine first the molar mass of air. To do this we multiply the mole percent of each by their respective molar masses:
    N2: 0.78 * 28 g/mol = 21.84 g N2 / mol air
    O2: 0.21 * 32 g/mol = 6.72 g O2 / mol air
    Ar: 0.01 * 40 g/mol = 0.4 g Ar / mol air
    21.84 + 6.72 + 0.4 = 28.96 g / mol air

    Now that we know the molar mass, we divide the 1 kg of air by the molar mass:
    1000 g air / (28.96 g / mol air)
    = 34.53 mol air

    Hope this helps~ :)

  • chemistry -

    That is excellent thank you. Now you have given me the answer working through it myself makes a lot more sense.

    Can you help me with the one below as well.

    A 25.0 mL solution of HCl has been spilt. It took 21.8 mL of saturated 2.5 M NaOH to neutralise the acid. What was the molar concentration of the acid?

  • chemistry -

    If the volume is split, then the amount of moles will be split as well. However, the mole to volume ratio will not change in a homogenous mixture. So, the molarity can be solved using MV=MV


    Answer contains 2 significant figures.

  • To Sarah--chemistry -

    I worked that HCl/NaOH problem for you before you posted the air question.

  • To Devron--chemistry -

    I think you misinterpreted Sarah's question. I believe spilt, in Sarah's culture, means spilled in ours (and not split). I think her question is just a "titration" question. My response is below at an earlier post.

  • chemistry=>Dr.Bob222 -


  • chemistry=>Dr.Bob222 -

    I was wondering why the individual ask the question when it seemed kind of straight forward. Sometimes I want to answer a question, but I am not sure what they are asking, or I'm not sure concerning the concept if I haven't done a particular type of problem in a while. So, I just don't respond, and I decide to let you or someone else handle the problem. I figured that some of the questions come from individuals that speak english as their second language, or are from people studying science in places outside the US because some of the questions that I see posted are not questions that you will typically see in a chem. science book in America (e.g. analytical chem. problem earlier last week with an apparatus on the right). But I answer the questions if I think I can, or I have an idea on how to solve them because science is science, and I like to help people learn science because science is fun.

  • chemistry -

    I do mean spilled, thanks.

  • To Devron--chemistry -

    I have learned through experience that students in the UK use spilt while US uses spilled. Same thing for spelling colour or odour or sulphur etc. Canadian students spell the same as the British. I don't know if Sarah is Canadian but UK for sure. The aussies are UK also. For those strange analytical chemistry question, I agree. Some are clearly worded wrong but most of those who speak English use the British system; i.e., India, Pakistan, etc. Therefore, some of those look a little different for two reasons (1) English is a second language and sentence structure is not the best (2) what little English they do speak is British. Remember, however, that many of the U.S.students don't do much better. Many U.S. students are confused, too, and their sentence structure is so poor sometimes I have no idea what they've asked.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. sci/chemistry

    when 1.87 g of gypsum(hydrated calcium sulfate) was heated to constant mass, it lost 0.39 g of water. What is the formula of gypsum?
  2. chemistry

    hot-air balloon is filled with air at a volume of 3.64 x 10^3 m^3 at 745 torr at 39C. the air in balloon is heated to 60C, causing balloon to expand to a volume of 4.50x 10^3 m^3. what is the ratio of the number of moles of the air …
  3. chemistry

    Calculate the number of grams of reactant left over when 28.35 grams of silver reacts with 50.0 liters of air at STP which is 20.9476 % oxygen by volume. The density of air at STP is 1.292 g/L. attemt at a solution: m = dv = 64.6 g …
  4. chemistry 11

    Hi, I am stuck on a couple questions in chemistry 11. The questions are 1. Calculate the number of moles of the anhydrous salt left behind 2. Calculate the number of moles of water removed by heat from your sample of hydrate. 3. Calculate …
  5. phisic

    Treating air as an ideal gas of diatomic molecules, calculate how much heat is required to raise the temperature of the air in an 7.47 m by 14.9 m by 2.87 m room from 19.9°C to 21.7°C at 101 kPa. Neglect the change in the number …
  6. Chemistry

    Calculate the number of moles of Co^+2 are there in the equation Co(H2O)6^+2 +4Cl <--> CoCl4^-2 +6H2O?
  7. Physics

    Calculate the ideal gas constant using the moles of air, temperature of air and slope of the air vs. 1/Pressure graph. Moles of air = 4.89*10^-4 Temperature of air = 23C Slope = 2317
  8. chemistry

    Suppose you designed an experiment in which you burned a known quantity of magnesium in air. You used the product to determine how many moles of oxygen would react with the known number of moles of magnesium. Why would burning magnesium …
  9. Chemistry

    UMM.. I keep coming up with the wrong answer?
  10. AP Chemistry

    Suppose you designed an experiment in which you burned a known quantity of magnesium in air. You used the product to determine how many moles of oxygen would react with the known number of moles of magnesium. Why would burning magnesium …

More Similar Questions