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Physics gas equations hwk help

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    Hi,

    I'm a bit stuck with a couple of questions because I'm getting a bit confused about which formulae to use.

    1. Hydrogen molecule. Molar mass-0.002Kgmol-1. Temperature= 273k

    Calculate mean kinetic energy.
    Calculate root mean square speed.

    2. Air consists of mostly nitrogen and oxygen in proportions 1:4 by mass. Demonstrate that the Crms^2 of a nitrogen molecule in air is 1.07 times that of oxygen in same sample.

    Molar mass: Nitrogen: 0.028 Oxygen: 0.032

    Thanks
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    (Original post by VioletPhillippo)
    Hi,

    I'm a bit stuck with a couple of questions because I'm getting a bit confused about which formulae to use.

    1. Hydrogen molecule. Molar mass-0.002Kgmol-1. Temperature= 273k

    Calculate mean kinetic energy.
    Calculate root mean square speed.

    2. Air consists of mostly nitrogen and oxygen in proportions 1:4 by mass. Demonstrate that the Crms^2 of a nitrogen molecule in air is 1.07 times that of oxygen in same sample.

    Molar mass: Nitrogen: 0.028 Oxygen: 0.032

    Thanks
    1) Using the temperature determine the mean kinetic energy. (There's a simple equation for that in the textbook with a 3/2 in it)
    Use the equation (mean kinetic energy)=0.5*mass*(root mean square speed)^2 to find the root mean square speed

    2) Equate the kinetic energies of nitrogen and oxygen using the eon above, plug in the mass
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    (Original post by MathMoFarah)
    1) Using the temperature determine the mean kinetic energy. (There's a simple equation for that in the textbook with a 3/2 in it)
    Use the equation (mean kinetic energy)=0.5*mass*(root mean square speed)^2 to find the root mean square speed

    2) Equate the kinetic energies of nitrogen and oxygen using the eon above, plug in the mass
    Thanks, I've done no. 1 now but I think I'm still doing no. 2 wrong as I can't seem to get to 1.07.
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    (1/2)*0.028*v^2=1/2*0.032*c^2
    8/7c^2=v^2
    v=sqrt(8/7)c
    =2sqrt(2/7)c= 1.069044...c
    roughly 1.07c
    therefore
    v/c is roughly 1.07
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    (Original post by MathMoFarah)
    (1/2)*0.028*v^2=1/2*0.032*c^2
    8/7c^2=v^2
    v=sqrt(8/7)c
    =2sqrt(2/7)c= 1.069044...c
    roughly 1.07c
    therefore
    v/c is roughly 1.07
    Thanks, I was trying to do it without labelling one as v and one as c so I understand it much better now
 
 
 
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