Answer: It is true that Your friend should release the 
first.
Explanation:
The velocity of particles of a gas is inversely proportional to the mass of gas. This means that more is the mass of gas less will be its velocity.
Or, more will be the mass of gas more slowly it will move from one place to another.
The molar mass of chlorine gas is more than the molar mass of hydrogen gas. Therefore, chlorine gas will move slowly.
So, your friend should release the gas first and then according to the length of room you should release the 
gas.
Thus, we can conclude that it is true that Your friend should release the first.
6.4 times 10^-7 is the answer because you are moving your decimal places to the left so it will be negative 7
This problem is providing us with a statement in which we need to figure out the word fitting in the blank. At the end, after analyzing the information, the word turns out to be colligative as show below:
<h3>Colligative properties.</h3>
In chemistry, colligative properties of solutions account for the behavior of a solution with respect to the pure solvent, to which a solute is added.
Among them, we have boiling point elevation, freezing point depression, vapor pressure lowering and osmotic pressure, which are all affected by the concentration of the solute but not by the identity of the solute.
In such a way, we conclude that the correct word that fits in the blank is colligative as shown below:
"Colligative properties depend on the concentration of a solute in a solution but not on the identity of the solute."
Learn more about colligative properties: brainly.com/question/10323760
