Determining how compounds react

[Kalagaraz]

Is there any way to predict how two chemicals will react or is it up to experimentation to discover that?

Take salt + water for example:

NaCl + H₂O -> HCl + NaOH

The equation is balanced, but obviously when mixing salt and water you don't get hydrochloric acid...you get salt water... So how can you determine how compounds will react and would there be a way to induce the above reaction?

Sorry, just started learning chemistry like 15 minutes ago (to try and learn about chemiluminescence), and I apologize is this is a really newbie question.

 

[VeeEight]

Usually when first starting out you will learn how things react by practicing lots of problems (stoichiometry problems, strong/weak acids & bases, etc). If you take a course in Organic Chemistry, half of the time spent will be on how chemicals react based on their functional groups.

 

[Ygggdrasil]

One approach is to look at the thermodynamics of the reaction. You can look up the standard free energies of formation of the products and reactants and calculate the overall ΔG of the reaction. If the ΔG is very positive, the reaction is not going to happen (without the addition of an external source of work such as electricity).

While this approach will tell you whether the reaction obeys the laws of thermodynamics, there are other factors that determine reactivity, such as the rate of reaction. For example, the reaction diamond --> graphite has an overall negative ΔG at room temperature, but the rate of this reaction is so slow that it does not happen (hence, the saying that diamonds are forever).

 

[Borek]

While this approach will tell you whether the reaction obeys the laws of thermodynamics

Do you know one reaction that doesn't follow them?