Gen CHem SOlutions

1. Describing Solutions
4.2 | Electrolytes and Nonelectrolytes
4.3 | Equations for Ionic Reactions
4.4 | Introducing Acids and Bases
4.5 | Acid–Base Nomenclature
4.6 | Double Replacement
(Metathesis) Reactions
4.7 | Molarity
4.8 | Solution Stoichiometry
4.9 | Titrations and Chemical
Solutions and electrolytes
Acid-base reactions
Solutions; reactions
Lab: Get charged up
Precipitation reactions
Oxidation-reduction reactions
Balancing oxidation-reduction reactions
Thermochemistry I Lab: Proof it
Energy, enthalpy, heating, and cooling
Calorimetry: measuring heat
Enthalpies of formation and reaction
Reci: Thermochemistry II
Lab: Proof it Feb 20 Enthalpies of reaction and Hess’s Law
Solution: Solutions are homogenous mixtures with contain two or more substances. A solution
has uniform composition.
Examples are sugar and table salt in water.
The dissolving medium (water) is the solvent and the dissolved substances (sugar or salt) is the solute. If
both components in a solution are 50%, the term solute can be assigned to either component. When gas
or solid material dissolves in a liquid, the gas or solid material is called the solute. When two liquids
dissolve each other, the major component is called the solvent and the minor component is called the
solute.
Example2: air we breathe, the liquids we drink, and the fluids in our body are all solutions.
Solute: Solute is a substance dissolved in solvent. It can be gas, liquid or Solid
Example: CO2 in soda, Liquid—ethylene glycol in antifreeze and Solid—sugar in syrup
Solvent: Solvent is a Medium that dissolves solutes. It is a Component that is present in largest amount
in a solution. Can be gas, liquid, or solid.
Example: Aqueous solution—water is solvent
Universal Solvent: Water is sometimes called the universal solvent because of its ability to dissolve a
diverse array of substances. Acetone is also occasionally referred to as a universal solvent since it is able

2. to dissolve oils, alcohols, and water. In truth, however, there is no such thing as a universal solvent
because no one substance is capable of dissolving every possible solute.
Suspension: A heterogenous mixture of two or more substances is called a suspension.
For example, clay in water. In this case, suspended particles of the dispersed substance, clay, are
distributed nonuniformly in the medium. The bottom part of the mixture has more particles than the
upper.
Concentrated Solution: Solution that has large solute to solvent ratio(More solute)
Example: Pickle and Brine
Percentage concentration: It is the number of grams of solute per 100 g of solution, a “solute-to-
solution” ratio.
Example: The concentration of sodium chloride in seawater is often given as 3% NaCl, which means 3 g
NaCl/100 g seawater.
Dilute Solution: Solution that contains less solute to solvent ratio(Less Solute)
Example: Eye drops

3. Electrolytes in Aqueous Solution: Solutions of ionic compounds and acids in water conduct electricity
because they produce ions. These substances are known as electrolytes. Electrolytes dissolve in water
and conduct electricity because they dissociate to form mobile, solvated cations and anions.
Examples: Sodium chloride and hydrochloric acid are electrolytes
Nonelectrolytes: Most of the covalent compounds stay as molecules in their solutions and do not
conduct electricity. Such substances are known as nonelectrolytes. Example: Sugar is an example of a
nonelectrolyte.
Nonelectrolytes do not conduct electricity when dissolved in water, because their molecules dissociate
into ions(water itself is a nonelectrolyte)
Electrolytes are divided into two categories:
Dissociation:

4. Dissociation is the separation of ions that occurs when a solid ionic compound dissolves. Salts break
apart into ions when entering solution breaking apart) of the ionic compound.
It is important to remember chemical equations of dissociation reaction.
The subscripts for the ions in the chemical formulas become the coefficients of the respective ions on
the product side of the equation.
Example: Dissociation of an ionic compound as it dissolves in water. Ions separate from the solid and
become surrounded by water molecules. The ions are said to be hydrated.
The formula unit of sodium chloride dissociates into one sodium ion and one
chloride ion. The calcium nitrate formula unit dissociates into one calcium ion and
two nitrate ions. This is because of the 2+ charge of the calcium ion. Two nitrate
ions, each with a 1− charge are required to make the equation balance
electrically. The ammonium phosphate formula unit dissociates into three
ammonium ions and one phosphate ion. Note that the polyatomic ions themselves
do not dissociate further, but remain intact.
Do not confuse the subscripts of the atoms within the polyatomic ion for the
subscripts that result from the crisscrossing of the charges that make the original
compound neutral. The 3 subscript of the nitrate ion and the 4 subscript of the
ammonium ion are part of the polyatomic ion and simply remain as part of its
formula after the compound dissociates. Notice that the compounds are solids
(s) which then become ions in aqueous solution (aq).
Hydrated ions:

5. Writing the Equation for the Dissociation of an Ionic Compound
Ammonium sulfate is used as a fertilizer to supply nitrogen to crops. Write the equation for the
dissociation of this compound when it dissolves in water.
Solution: In this case, the cation is NH4 + (ammonium ion) and the anion is SO4 2- (sulfate ion). The
correct formula of the compound is therefore (NH4)2SO4, which means there are two NH4 + ions for
each SO4 2- ion. We have to be sure to indicate this in the ionic equation. We write the formula for the
solid on the left of the equation and indicate its state by (s). The ions are written on the right side of the
equation and are shown to be in aqueous solution by the symbol (aq) following their formulas.

6. Precipitation: The chemical reaction that produces a precipitate is called a precipitation. A precipitation
equation is essentially the reverse of a dissociation equation – it shows the formation of a solid
substance from the combination of ions in solution. The ionic solid formed is the single product and the
aqueous ions are the reactants.
These equations, like all equations, must be balanced. Showing the physical state of each species is
critical.

7. Ba2+(aq) + SO4 2− (aq) → BaSO4(s)

8. Saturated Solution: When a solution contains as much solute as it will hold at a given temperature, it is
a saturated solution. A solution that has reached the maximum solubility is called a saturated solution.
Unsaturated solution - Solution containing less solute than maximum amount . That means it can hold
more solute.
Supersaturated Solution: Supersaturated solutions are solutions that have dissolved solute beyond the
normal saturation point. Supersaturated solutions are unstable and can only be prepared if there are no
solids present. For example, sodium acetate has a very high solubility at 270 K. When cooled, such a
solution stays dissolved in what is called a meta-stable state.
Solubility of a solution: The solubility of a solute is the amount required to give a saturated solution.

9. Equations for Ionic Reactions
Ionic compounds react with each other when their aqueous solutions are combined.
example, when solutions of lead(II) nitrate, Pb(NO3)2, and potassium iodide, KI, are mixed, a bright
yellow precipitate of lead(II) iodide, PbI2, forms (Figure 5.7). The chemical equation for the reaction is:
In this reaction,we have noted the insolubility of PbI2 by writing (s) following its formula. This is called a
molecular equation because all the formulas are written with the ions.
Writing Molecular, Ionic, and Net Ionic Equations
Write the molecular, ionic, and net ionic equations for the reaction of aqueous solutions of lead(II)
acetate and sodium iodide, which yields a precipitate of lead(II) iodide and leaves the compound sodium
acetate in solution.
Solution: We have: Reactants Products lead(II) acetate Pb(C2H3O2)2 lead(II) iodide PbI2 sodium iodide
NaI sodium acetate NaC2H3O2
The Molecular Equation We assemble the chemical formulas into the molecular equation and balance
it.
Notice that we’ve indicated which substances are in solution and which substance is a precipitate. This is
the balanced molecular equation.

10. The Ionic Equation
To write the ionic equation, we write the formulas of all soluble salts in dissociated form and the
formulas of precipitates in “molecular” form.
We are careful to use the subscripts and coefficients in the molecular equation to properly obtain the
coefficients of the ions in the ionic equation.
This is the balanced ionic equation. Notice that to properly write the ionic equation it is necessary to
know both the formulas and charges of the ions.
The Net Ionic Equation We obtain the net ionic equation from the ionic equation by eliminating
spectator ions, which are Na+ and C2H3O2 - (they’re the same on both sides of the arrow). Let’s cross
them out.
Notice that this is the same net ionic equation as in the reaction of lead(II) nitrate with potassium iodide.

16. Acids and Bases

18. Arrhenius’ Definition of Acids and Bases
An acid is a substance that reacts with water to produce hydronium ion, H3O+. A base is a substance
that produces hydroxide ion, OH-, in water.

19. Formation of H3O+ by Acids
In general, acids are molecular substances that react with water to produce ions, one of which is H3O+.
For example, when gaseous molecular HCl dissolves in water, a hydrogen ion (H+) transfers from the HCl
molecule to a water molecule. Write equations that show the dissociation of the following compounds
in water: (a) CaI2 and (b) potassium phosphate. (Hint: Identify the ions present in each compound.)
Write equations that show what happens when the following solid ionic compounds dissolve in water:
(a) Al(NO3)3 and (b) sodium carbonate
4.1
Write equations that show the dissociation of the following compounds in water:
(a) CaI2 and (b) potassium phosphate. (Hint: Identify the ions present in each compound.) 4.2
4.2
Write equations that show what happens when the following solid ionic compounds dissolve in water:
(a) Al(NO3)3 and (b) sodium carbonate

20. 4.3
When solutions of (NH4)2SO4 and Ba(NO3)2 are mixed, a precipitate of BaSO4 forms, leaving soluble
NH4NO3 in the solution. Write the molecular, ionic, and net ionic equations for the reaction. (Hint:
Remember that polyatomic ions do not break apart when ionic compounds dissolve in water.)
4.4
Write molecular, ionic, and net ionic equations for the reaction of aqueous solutions of cadmium
chloride and sodium sulfide to give a precipitate of cadmium sulfide and a solution of sodium chloride
4.5 Propanoic acid, HC3H7O2, is only slightly ionized when dissolved in water. Write the appropriate
chemical equation to describe this statement. (Hint: Use acetic acid as a guide.)
4.6 Nitric acid, HNO3, is a strong acid that can be used to make explosives. Nitrous acid, HNO2, is a weak
acid thought to be responsible for certain cancers of the intestinal system. Write the chemical equations
that show the ionization of these two acids in water.
4.7Triethylamine, (C2H5)3N, is a base in water. Write an equation for its reaction with the solvent. (Hint:
How do nitrogen-containing bases react toward water?)
4.8
4.9

21. Citric acid is the acid in citrus fruits such as lemons, limes, and oranges. Write equations for the stepwise
ionization of citric acid, H3C6H5O7, in water. (Hint: Determine how many of the hydrogen atoms will
ionize.)
4.10 : Hydrogen sulfide is responsible for the smell of rotten eggs, and dissolves in water to form
hydrosulfuric acid. Write the stepwise ionization equations for aqueous hydrosulfuric acid, H2S(aq).
4.15:
Write the molecular, ionic, and net ionic equations for the neutralization of HNO3(aq) by Ca(OH)2(aq).
(Hint: First determine whether the acid and base are strong or weak.)
4.16:Write molecular, ionic, and net ionic equations for the reaction of (a) HCl with KOH and (b) barium
hydroxide with hydrochloric acid.
4.17:Write molecular, ionic, and net ionic equations for the reaction of the weak base methylamine,
CH3NH2, with formic acid, HCHO2 (a weak acid).
4.18: What is the formula for the product of the reaction of one mole of NaOH with one mole of
sulfurous acid? What is the name for this compound? (Hint: What information do we get from the prefix
bi- and the suffix -ite?)
4.19:Write molecular equations for the stepwise neutralization of arsenic acid by sodium hydroxide.
What are the names of the salts that are formed? Identify the step in which the acid is completely
neutralized
4.20:

22. Knowing that salts of the formate ion, CHO2 -, are water soluble, predict the reaction between Co(OH)2
and formic acid, HCHO2.
4.21: Write molecular, ionic, and net ionic equations. (Hint: Apply the tools we used in Example 4.7.)
Show that in aqueous solutions there is no net reaction between MgCl2 and (NH4)2SO4.