Achieve HW #17

[Shane_Yu_3K]

Hello,

Can anyone explain how to do Achieve HW #17? Why do I have to divide the molar mass of nitrogen by the Avogadro's constant?

Thank you!

[Ashley Tonthat 2B]

Hi Shane,

The reason you have to divide by Avogadro’s number is because you want your mass to be in terms of kg per molecule, not kg per mole. You use the molar mass of nitrogen to get the grams of nitrogen, but the molar mass is in terms of grams per mole. Since there are 6.022 x 10^23 molecules in 1 mole, you use this conversion factor to get the mass in grams per molecule. Hope this helps.

[Jiane_Beach_1D]

You have to divide the molar mass by Avogadro's constant because the question asks for the average wavelength of a single molecule. In a diatomic nitrogen molecule there are approximately 28 grams in a mole. In one mole there are 6.0221 *10^23 molecules. To figure out how many grams each molecule weighs you must divide to get the correct mass for your equation.

[Kiku Shirakata 2A]

Hello,
For calculation problems, I always find it easier to make sense of it what's going on by looking at and following the units. We know that we want to end with meters at the end, so if you write all the units for planck's constant (Js), mass(kg), and velocity(m/s), they should all cancel out to become meters.
To solve this problem, we use the equation, wavelength=h/(mass*velocity). We know what planck's constant is, velocity, and mass (molar mass/Avogadro's number).

[Nico Towfighian 3L]

The molar mass if the mass of 1 mole of the subject, dividing by avacadros number makes it so you can find the mass of a singular particle of that element

[Mason_Hoppe_1A]

Ok so it makes sense that we would need to divide the molar mass of the element by Avagadro's number and then multiply this number by two (as it is a diatomic molecule). The only remaining steps would be to multiply this number (ensuring that it is in kilograms) (the mass of the diatomic molecule) by the given velocity to attain the value of the momentum, and then to divide this momentum by Planck's constant correct?

I ask because these are the steps I have followed yet my answer is incorrect on Achieve, (I have checked my calculations a few times), so I think I am missing something. Is lambda=h/mv (lambda=h/p) the incorrect equation?

[Allison Mercado-3F]

Hi I have this problem and cannot solve it still. Any help is appreciated !
The average speed of a diatomic nitrogen molecule at 25 ∘C
is 515.2 m⋅s−1
. What is the average wavelength of a nitrogen molecule at this temperature? Assume that the molecule acts as a single particle.

[Skylar Lo 2C]

You would have to divide by Avogadro's constant because it asks for per molecule instead of per mole.Just one more conversion.

[Edwin Montalvo 1G]

We have to divide by Avogadro's number because we want to have the units in kg / molecule, not kg / mole. If we have kg / mol, we need to multiply by (6.022 x 10^23 molecules) / 1 mole to get our answer into kg/molecule. Hope this helps!

[Nick Oscarson 1K]

You must divide the molar mass of nitrogen by Avogadro's constant because you're trying to find the mass in kg per molecule, not per mole. With this information, just take the molar mass of nitrogen in kg and divide by 6.022 x 10^23, then use this mass for part of the equation.

[Maggie Messer 1A]

You divide by Avogadro’s # because the question is asking for atoms/molecules, not moles for the units!