Which statement is true according to the kinetic theory?
molecules of different gases with the same mass and temperature always have the same average density.
molecules of different gases with the same mass and temperature always have the same average volume.
molecules of different gases with the same mass and temperature always have the same pressure.
molecules of different gases with the same mass and temperature always have the same molecular mass.
molecules of different gases with the same mass and temperature always have the same average kinetic energy.
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The true statement is that different gases with the same mass and temperature always have the same average kinetic energy. This is one of the postulates of the kinetic theory of matter.

If we two objects A and B, they will have mass and and velocity and respectively. If . Then it follows that

. Since the mass is the same it means the velocity of the two objects should be the same so that they have the same average kinetic energy.

E. Molecules of different gases with the same mass and temperature always have the same average kinetic energy.

Explanation: I got this right on Edmentum.

84 g of N₂        

Explanation:

We begin from the reaction:

N₂O₄  +  2N₂H₄ →  3N₂  + 4H₂O

  1st step: Find out the limiting reactant.

We convert the mass to moles.

       276 g . 1mol/ 92g = 3 moles of N₂O₄

64 g . 1mol / 32g = 2 moles of hidrazine  

Limiting reactant is the hydrazine. Ratio is 1:2, then for 3 moles of tetroixde I may need 6 moles of N₂H₄. (But I only have 2).

To determine the grams of produced nitrogen we see stoichiometry (2:3)    

2 moles of hydrazine can produce 3 moles of N₂

Definetaly our 2 moles make 3 moles of gas.

We convert the moles to mass.

3 mol . 28g /1mol = 84 g of N₂