The formation of chemical bonds from separation atoms?

Question

A) is always exothermic
B) is always endothermic
C) is never spontaneous
D) may be either endothermic or exothermic
E) increases entropy

Answer 1

Not sure the level with which you are learning, so feel free to ignore the thermodynamics explanation. If you just want to answer the question, select D.

Like most test questions, there is not enough conditions specified and truly, we could choose several anwers, but only after making assumptions that less likely to be in the testers mind. I will assume a high school or intro level college course because above that this should be challenged as too vague.

Use logic to realize that answer choice C is not true. Evaluating the others we realize that A means only heat is given off when bonds form and B means heat is absorbed or added during the formation of bonds. D means conditions exist in which either situation is possible and E means that final product is in a state that has a higher value for entropy. This only holds true when both Temp and pressure of a system is held constant, but we will eliminate later as well.

Basically a bond can occur when the system goes from a high energy state to a lower energy state. Formation of bonds is essentially a chemical reaction. The Gibbs Free Energy equation:

(delta)G=(delta)H-T(delta)S

T=temp of system in Kelvin
(delta)H is the heat energy change
(delta)S is the change in entropy (disorder)

defines whether a reaction will occur spontaneously or not. (deltaG) must be negative for this to be true. So we will assume
using this equation and recognizing that (delta)H tells us exo or endothermic if it is positive or negative , examination of the possibilities of (delta)H and (delta)S,

If (delta)H is negative and (delta)S is positive the equation will result in a negative value for (delta)G which means a favorible condition exists for bonding to occur. Therefore, the condition of (delta)H negative (energy leaves as heat - exothermic) is true. We can thus eliminate answer choice B.

If the opposite is true and (delta)H is positive and (delta)S is negative, the result is (delta)G that is positive and therefore not spontaneous. no reaction or bonding occurs.

If both (delta)H is positive and (delta)S is positive, only a large enough (delta)S will overcome the positive (delta)H in the equation. So if both are positive and T(delta)S is greater than (delta)H the bonding will occur. Therefore, when (delta)H is positive (endothermic) the reaction may occur as well. We can thus eliminate choice A.

We have shown that C is a true statement because conditions can be met in which the reaction is both exo or endothermic. However, please note that in both conditions (delta)S is also positive, indicating an increase in entropy. For the most part any system will always trend toward an insrease in entropy.

The question then arises, what happens when (delta)S is negative (decreased entropy) and (delta)H is negative. For most situations T(delta)S will be large enough to create a positive (delta)G from our equation. In very rare cases will (delta)H - T(delta)S result in a negative answer. However, the equation shows this as a possibility when (delta)G= large negative (delta)H - T x small negative (delta)S => large negative # minus a smaller negative => larger negative + smaller # = negative. (Hope you follow my train of thought). Therefore in the right situation - (delta) can be negative and bonding/reaction can occur when entropy decreases. Eliminate E and C is the correct answer.

Careful what you ask for. Wikipedia site looks pretty informative but very detailed and you have to use a few different pages.

Answer 2

a million.Ionization Enthalpy (potential): Lesser the price of ionization enthalpy, more effective the tendency of the atom to kind cation. as an example, alkali metals kind cations actual because of the low value of ionization energies. 2. Electron income enthalpy: more effective the price of electron income enthalpy, extra the tendency of the atom to kind anion .as an example ,halogens have severe electron income enthalpies interior the respective classes and kind ionic compounds actual . 3. Lattice enthalpy: that is the potential released even as the close packing of the gaseous ions of the different value varieties one mole of ionic strong. value of lattice potential provides an idea about the inter-ionic forces and it also provides the degree of the steadiness of the ionic compound which relies upon upon good the following factors. 4. length of the ions—Smaller the length of the ion s, lesser the inter nuclear distance and bigger the inter ionic interaction, for this reason, more effective the price of lattice potential 5.value on the ions--- more effective the price of the price on the ions more effective stands proud because the appealing forces and better the adverse value of lattice potential.

Answer 3

Bond formation is always exothermic.