2H2 (g) + O2 (g) -->2H2 O(g)
mole ratio of H2:O2=2:1
7.25/2=3.625
A force of attraction that
holds atom together
When atoms react they form a
chemical bond which is defined as a force of attraction that holds atom
together. A force of attraction is defined as a kind of force that draws two or
more objects together regardless of distance. There are two major categories of
forces of attraction, one is intramolecular and intermolecular. Intramolecular forces
is the presence of forces in atoms internally. While intermolecular is the
force by which the force that is existent in two or more elements.
A is obviously out because it leads to a volume of 125.0 milliliters of the new solution and gives you a lower concentration than you were aiming for.
D is out because you are adding 75 milliliters of the stock solution, so your concentration would be too high. You only need 25.0 milometers of stock solution per 100 milliliters of the new solution.
C is also out because it leads to 50.0 milliliters stock solution per 100 milliliters of the new solution and hence the wrong concentration.
B is by default the correct answer. It also details the correct technique. First you add the stock solution (This you know from your calculations to be 25 milliliters.) then you add the water up to the volume you needed. (Because the calculations only tell you the total volume of water not what you need to add) You also add the water last so you can rinse the neck of the flask to make sure you also get all the stock solution residue into the stock solution.
I would add the final step of stirring, but B is the only answer that can be correct.
This is seen in the first law of Thermodynamics stating that matter and energy cannot be destroyed nor created.
