Review for Chapter 4
1. A solution is a homogeneous mixture of two or more substances.
A solute is the substance present in the smaller amount in a solution.
A solvent is the substance present in the larger amount in a solution.
2. An electrolyte is a substance that when dissolved in water enables the solution to conduct
electricity.
A strong electrolyte results from a compound that dissociates completely into ions in water.
A weak electrolyte results from a compound that dissociates into ions to a limited degree in
water.
A nonelectrolyte does not dissociate into ions or conduct electricity when dissolved in water.
3. Hydration is the process in which an ion is surrounded by water molecules arranged in a
specific manner.
4. A precipitation reaction may occur when two ionic compounds are mixed in solution and a
cation and anion react to form an insoluble product. Know how to use the solubility rules
found in Table 4.2 to determine if a compound will be soluble or insoluble in water.
5. Know how to write the molecular equation, ionic equation, and net ionic equation for a
precipitation reaction.
6. Spectator ions are ions that are not directly involved in the reaction taking place in solution.
7. Arrhenius acid: a substance that ionizes in water to produce H+ ions
Arrhenius base: a substance that ionizes in water to produce OH- ions
Bronsted acid: a proton donor
Bronsted base: a proton acceptor
8. A hydronium ion, H3O+, is a proton plus a water molecule.
9. A monoprotic acid yields one hydrogen ion, H+, when ionized. Example: HCl
A diprotic acid yields two hydrogen ions, 2H+, when ionized. Example: H2SO4
A triprotic acid yields three hydrogen ions, 3H+, when ionized. Example: H3PO4
10. A neutralization reaction occurs when an acid and a base react. Neutralization reactions
produce a combination of H2O(l), a salt, and/or a gas.
11. Oxidation-reduction reactions are reactions involving the transfer of electrons.
The reducing agent donates electrons.
The oxidizing agent accepts electrons.
12. The oxidation number or oxidation state signifies the number of charges an atom would
have in a molecule or ionic compound if electrons were transferred completely.
13. Know the following rules for assigning oxidation numbers:
In free elements, each atom has an oxidation number of 0.
For ions composed of only one atom, the oxidation number is equal to the charge on the ion.
The oxidation number of oxygen in most compounds is -2 (but is -1 in H2O2 or O22-).
The oxidation number of hydrogen is +1, except when it is bonded to metals in binary compounds such as LiH
where its oxidation number is -1.
Fluorine has an oxidation number of -1 in all its compounds.
In a neutral molecule, the sum of the oxidation numbers of all atoms must be zero.
In an ion, the sum of oxidation numbers of all the elements in the ion must be equal to the net charge of the ion.
Oxidation numbers are usually but not always integers (for example, O in O 2- has an oxidation number of -1/2).
14. Be able to identify the following types of redox reactions:
Combination reaction
Decomposition reaction
Combustion reaction
Ex: S(s) + O2(g)  SO2(g)
Ex: 2NaH(s)  2Na(s) + H2(g)
Ex: C3H8(g) + 5O2(g)  3CO2(g) + 4H2O (l)
Displacement reaction (3 types: hydrogen, metal, halogen)
Hydrogen displacement Ex: Ca(s) + 2H2O(l)  Ca(OH)2(s) + H2(g)
Metal displacement
Ex: TiCl4(g) + 2Mg(l)  Ti(s) + 2MgCl2(l)
Halogen displacement Ex: Cl2(g) + 2NaI(aq)  I2(s) + 2NaCl(aq)
-1
-2
0
 oxidation number on oxygen
Disproportionation reaction Ex: 2H2O2(aq)  2H2O(l) + O2(g)
15. Know how to use an activity series for metals (Figure 4.16) to determine if a displacement
reaction will occur.
16. Know the activity series for halogen displacement reactions: F2 > Cl2 > Br2 > I2 and
be able to determine if a halogen displacement reaction will occur.
17. Molarity or molar concentration is defined as:
M = moles of solute = n
liters of solution V
Units: moles
L
Know how to calculate the molarity of a solution.
18. Dilution is the procedure for preparing a less concentrated solution from a more
concentrated solution.
MiVi = MfVf
since the moles of solute before dilution = moles of solute after dilution
Know how to calculate how much additional water would be needed to dilute a solution to a
specified concentration.
19. Gravimetric analysis is an analytical technique based on the measurement of mass.
20. Titration is a process in which a solution of accurately known concentration is added
gradually to a solution of unknown concentration until the chemical reaction between the two
solutions is complete. The unknown concentration can then be determined.
21. The equivalence point is the point at which the two solutions have completely reacted in a
titration. An indicator is a substance used to signal the equivalence point in a titration,
usually by a sharp color change.