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4 -- Part 1: Chemical Reactions
Some General Principles Aqueous Solutions: Titrations of each are provided.
If you want to know if a precipitate forms in a given reaction in solution, use the solubility guidelines.
Write chemical equations for reactions involving acids and bases if you know the common strong acids and bases.
Determine whether a redox process occurs by identifying the oxidation states of all elements in a reaction.
The half-equation method can be used to determine the balanced equation for a redox reaction.
Distinguish between reducing and oxidizing agents.
The molarity of a solution can be calculated using titration data.
A blue cloud of solid cobalt(II) hydroxide is formed when clear, colorless solutions of cobalt(II) chloride and sodium hydroxide are mixed.
There are three types of precipitation reactions considered in this chapter.
The majority of reactions in the general chemistry laboratory are carried out in solutions with water as the solvent.
Aqueous solutions can be used to bring together accurately measured amounts of reactants.
The goal of this chapter is to understand the nature of the substances involved, the changes that occur in these substances, and the way each reaction occurs.
Let's try to create a mental image of a solution at the molecule level.
The mental image of water might look something like Figure 5-1(a).
It is useful to look at the nature of the solutions in a bit more detail because we will encounter them throughout the chapter.
If the concentration of ion is not too low, the solution will conduct electricity.
An ion solution conducts electricity because the ion's move independently of each other, carrying a certain amount of charge.
The way in which electric current is generated is suggested by Figure 5-2.
The water molecule separated from the external source.
A conductor of electricity depends on the nature of the solute in the solution and the tendencies of the strong and weak electrolytes.
Pure water doesn't have the tendency to provide duct electric current.
A weak electrolyte makes the solution an electrical conductor when some solutes produce ion in solution.
There are sulfates that do not provide ion.
Not all electrolytes provide the same amount of ion in water.
The centration of the electrolyte is summarized in Figure 6-3.
If some are present, their concentration is very low.
The solution can be either a nonelectrolyte solution or a very dilute solution of an electrolyte.
The concentration of ion in solution is high.
Magnesium chloride is completely ionized in water.
The concentration of ion is low.
The solution could be a solution of a weak electrolyte, such as acetic acid, or it could be a solution of a strong electrolyte.
The molecule are ionized.
The solution of CH3COOH is a conductor of electricity.
The following generalizations can help you decide if a partic background and only ular solute is most likely to be a nonelectrolyte.
Weak electrolytes are one of the three types of molecular compounds.
There are no ion present in (a).
Richard Megna/Fundamental Photographs CH3OH is a nonelectrolyte.
The solute is almost 888-609- 888-609- 888-609- 888-609- 888-609- 888-609- There is a strong electrolyte in the solution.
A small fraction of the CH3COOH molecule ionize, even though most of the solute is present.
Dis sociation or ionization is one of the two processes that produce ion in solution.
The two terms have slightly different meanings.
An ionic compound can produce ion in solution by dissociation.
If a compound produces an ion in solution, it is by ionization.
The typi cally is arranged in a regular pattern as suggested by Figure 5-5.
We talked about the compound dissolving, the ion and molecule separated, and the water molecule rounded the ion and molecule.
Section 3-1 describes compounds that are surrounded by water.
The dissolution of an ionic solid to provide hydrated ion is called dissociation because the ion are initially present in the solid, and they become separated from one another as the solid dissolving.
In the presence of water, the formula units of MgCl2 completely dissociate into the separate ion.
The situation is more complicated for compounds with no ion present.
The KEEP IN MIND ion are created by a reaction of the compound with the water.
The double arrow D indicates that the reaction proceeds to a limited extent the H and O atoms.
A group that ionizes.
O was arranged in a pattern.
CH COO-(aq) + CH3 or H+(aq)
The Union of Pure and Applied has a hydrogen ion H+ attached to a water mole.
H3O+ ion is referred to as Figure 6-7.
This recommendation cannot be used to write equation (5.2) in a simpler way by eliminating a water molecule yet being universally adopted from each side of the equation: by chemists.
The CH3 Equations represent the ionization of CH COOH in water.
The first equation emphasizes that the H+ ion is firmly attached to a water molecule and that the ion is generated by a reaction involving water.
A useful notation for solution concentrations can be introduced with this new information.
We assume that the MgCl2 is completely dissolved into the ionosphere in a solution of 50 M.
There is a special symbol for the concentration of a species in solution.
The concentration of the species within the brackets is defined by the statement 3Mg2+4.
It is done here to emphasize that there is essentially no, because we don't usually write expressions like that.
The example shows how to calculate the concentrations of ion in a strong solution.
A good approximation is to say that a strong electrolyte is completely dissociated into individual ion in a solution.
At the low solution concentrations we will be using, we assume complete dissociation won't affect our results.
Calculating Ion Concentrations in a solution of a strong electrolyte is an example.
The solute has a strong electrolyte.
It is completely immersed in water.
The equation below shows the dissociation of Al21SO423.
The concentrations of the ion will always be multiples of the electrolyte's molarity.
We have 3Mg2+4 in the amount of 0.0165 M and 3Cl-4 in the amount of 0.0165 M.
Seawater is between 0.438 and 0.0512 M NaCl.
A water treatment plant adds fluoride to the water.
Some metal salts, such as NaCl, can be found in water, while others, such as AgCl, can't be found in water at all.
In industry, precipitation reactions are used to make many chemicals.
The first step in the test is the addition of magnesium metal from the water.
The objective is to represent precipitation reactions by chemical equations and to apply simple rules to confirm the presence of Cl-.
There is a contradiction between the equation and something we learned earlier in the chapter.
The "whole formula" form of the equation is called the "ionic" form.
The ion go through the reaction unchanged.
Solid consists of ion, we Ag+1aq2, and whole formulas are written for AgI(s).
Net ionic equations include a net in the formula.
The ionic equation needs to be balanced for the number of atoms in AgI(s), not Ag+I-1s2.
Both sides of the equation must have the same net electric charge.
Most chemical reactions will be represented by net ionic equations throughout the rest of the chapter.
Suppose we are asked if precipitation occurs when the solutions are mixed.
It is a good idea to rewrite the expression in the ionic form.
There are only two options.
Either a cation-anion combination leads to an insoluble solid or there is no reaction at all.
We need to know which ionic compounds are water insoluble and which are water insoluble to predict what will happen.
We expect the insoluble ones to form when the appropriate ion are present.
There are some guidelines that work for the majority of common ionic solutes.
Table 5.1 contains a concise form of these guidelines.
When two guidelines are in conflict, follow the lower-numbered guideline.
The water leads to the correct prediction in most cases.
We 4 cation are notsoluble for practical purposes.
They are notsoluble.
Salts of silver, lead, and mercury are notsoluble.
bromides, bromides, and iodides are notsoluble.
Thesulfides of group 2 cations and hydroxides are insoluble.
Sulfates are notsoluble for calcium, strontium, and barium.
When two ionic numbered guidelines take precedence in cases of a conflict, the guidelines from Table 5.1 are applied in the order listed.
According to compounds form a solid, AgBr(s) is insoluble in water and KNO31s2 is exchanging cations.
Predict what will happen in the following cases.
Write a net ionic equation if it's true.
The compounds shown in (a), (b), and (c) provide ion in solution.
The solubility guidelines in Table 5.1 can be used to determine whether the positive and negative ion from one compound combine to form an insoluble compound.
All ion remain in solution if onlysoluble compounds are formed.
If an insoluble compound is formed, it will leave the solution.
The net ionic equation for the precipitation reaction is obtained by removing the spectator ion from the full ionic equation.
Apply the strategy described above for each of them.
There is an insoluble compound produced by the and OH Mg2+ ion.
CuS is an insoluble compound.
There are no spectator ion in the equation.
Positive and negative ion combinations lead to watersoluble compounds.
There is no reaction.
It is illustrated for part a.
You should be able to go directly to a net ionic equation if you gain experience.
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