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.

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2