7.4 dissociation and Ionic Equations

Question 1

how are ionic compounds formed

Answer 1

ionic compounds are formed by the electrostatic attraction of two oppositely charged ions after electron transfer

Question 2

what is dissociation

Answer 2

Dissociation occurs when these ionic compounds dissolve in water and separate into charged ions

NaCl(s)→ Na+(aq)+ Cl-(aq)

What this is actually is the hydration of ions, making them aqueous (surrounded by water)

Question 3

what do covalent bonded molecules do in molecules

Answer 3

In contrast covalently bonded molecules will separate into individual, neutral molecules

Question 4

what 2 forces influence solvation

Answer 4

2 forces influence the solvation process for both types of molecules

1. van der Waals forces: weaker, in all interactions
2. polar forces: stronger, found in molecules exhibiting a significant charge separation

Question 5

what occurs in saturated solutions

Answer 5

Saturated solutionsare in a state of dynamic equilibrium, where there is a changing balance of undissolved and dissolved solutes. At the same time some compound solutes will be dissolving into ions, and separate ions will be recrystallizing into compounds

Question 6

how does saturated equilibrium occur

Answer 6

This occurs as the energy needed to maintain a solution state for dissolved particles is lost eventually as low velocity particles drop out of solution as undissolved solute. Other crystallized solute particles, initially kept from dissolving, may gain energy and enter the solution phase:

Question 7

what is precipitation

Answer 7

Precipitation reactions may occur if more solute is added to a saturated solution. Some combinations of solute cannot remain in a solution simultaneously and will join to form a precipitate (which is solid).

Question 8

what are hints to determine precipitates

Answer 8

Hints to determine precipitates

The question may tell you so, so read carefully.

· Use a Solubility Table, this is the quickest and easiest way!

· Do the reaction and find out empirically!

Question 9

what 3 chemical equations represent solvation

Answer 9

Many chemical reactions can be represented by three different kinds of equations: non-ionic equations, total ionic equations and net ionic equations.

Most aqueous reactions will be ionic due to dissociation

Question 10

what are non-ionic equations

Answer 10

In non-ionic equations, the elements and compounds are written in their molecular or formula unit forms. Example:

2 AgNO3(aq)+ BaCI2(aq)→2 AgCl(s)+ Ba(NO3)2(aq)

Question 11

what are total ionic equations

Answer 11

In total ionic equations, elements and compounds are written in the forms in which they are predominately present, electrolytes are written in ion form, and nonelectrolytes, precipitates and gases are written in their molecular or formula unit forms. Example:

2 Ag+(aq)+2 NO3-(aq)+Ba2+(aq)+2Cl-(aq)→ 2 AgCl(s)+Ba2+(aq)+ 2 NO3-(aq)

Question 12

what are net ionic equations

Answer 12

In net ionic equations, only those molecules, formula units or ions that have changed in form (i.e., predomin­ant reacting species) are included in the equation. Ions or molecules that do not change (spectator species) are omitted. Example:

2 Ag+(aq)+2Cl-(aq)→ 2 AgCl(s), which reduces to

Ag+(aq)+Cl-(aq)→ AgCl(s)

Question 13

what are the rules for net Ionic equations

Answer 13

The rules for net ionic equations are:
don’t include species that remain the same

Balanced in atoms and electrical charge, using lowest whole numbers

species written in form they actually exist in

Question 14

what can’t we have in solutions

Answer 14

There is no such thing as an ion in isolation, there will never be only Cl- ions in a solution, as there must be a positive ion from which it dissociated