Stock solutions of nitric acid have concentration of 16.0 m. what volume of stock solution is needed to prepare 2.00 l of 2.00 m solution of nitric acid by dilution with water?

0.083 L of concentrated 12.0M HNO3

This is a dilution chemistry problem. For problems like this one, use the following equation

M1V1=M2V2

Where
M1=molarity of solution 1
V1=volume of solution 1
M2=molarity of solution 2
V2=volume of solution 2

Whenever you dilute a concentrated stock solution, or for that matter, any solution, you are essentially changing the volume of that solution by adding water. If we look at what Molarity exactly is,

Molarity=moles1 Liter solution

you can see when you increase the volume, you decrease the molarity(concentration). In dilution cases, you are adding water so moles of the solute do not change, only the volume of the solution changes.

Using our equation from above, we can find the number of moles of nitric acid, HNO3, from what we are given.

We will let M1 and V1 be 8.0M and 125 mL respectively. Make sure to convert mLto L first. For M2, use the 12.0M. Isolate V2 and solve.

0.083 L

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.