How to describe most chemical reactions?

Question

A. Absorb energy

B. Occur at rates that are independent of temperature.

C. Are reversible

D. Produce precipitates

Answer 1

C describes them best. Most chemical reactions are actually equilibria that are pushed in one direction or the other depending on the presence of other reactants, catalyzers and external conditions.

Many reactions don't absorb energy, but are exothermic (eg combustion). Usually temerature plays a big part in determining the speed and feasibility of a reaction. Precipitates are only produced if the products are insoluble in the solvent at hand; this only occurs in a small number of reactions.

Answer 2

I would say C.

Most chemical reactions are indeed reversible. This is especially noticeable in equilibrium reactions where the slightest changes in temperature result in noticeable changes, like colour changes, heat emission, etc.

Not all absorb energy (feel cold). Some emit heat, some absorb heat.

Reaction rates are dependent on temperature. The temperature is a measurement of the average kinetic energy of a system (of each particle). If the temperature is high, it results in more frequent molecular collisions and also raises the energy of more particles to the required activation energy, which means more frequent, successful collisions. You can pretty much stop most reactions by cooling them down enough, though at absolute zero, reactions will theoretically stop, no matter what.

Not all reactions produce precipitates. This is mostly a product of reactions between solutions, while reactions include all between solids, liquids and gases.

Answer 3

Al chemical reaction are reversible A+B <> C  the direction of the reactions depends on the envirement and if the energielevel of C ore

A+ B is lower under this envirement conditions ( ph, temperature, pressure and other). The energielevel is lower on one side of the reaction if the entrophie is higher. Im I going too far? Is the entrophie in your head now higher?