Question

Study Guide Chapter 4

Students must be familiar with water as a solvent. Students must be familiar with the characteristics of water as a solvent. Is water the universal solvent? Why or why not? Is the water molecule polar? Why or why not?

Describe the process of hydration.

Define solubility. Do you expect sodium chloride to be soluble in water? Why or why not?   Is ethanol, CH₃CH₂OH, soluble in water? Why or why not? Is hexane, CH₃(CH₂)₄CH₃, soluble in water? Why or why not?

What is a polar bond? Does the water molecule has polar bonds?

Define solute, solvent, strong electrolyte, weak electrolyte and nonelectrolyte. Provide an example of each.

Define strong acids. What is the Arhenius definition of a strong acid? Of the following substances, which are strong acids, if any? CH₃COOH, HCl, CH₃OH, H₂SO₄, and HNO₃.

Define strong bases. Is KOH a strong base? Is NaOH a strong base?

What is a weak acid? Provide an example.

What is a weak base? Provide an example.

Define molarity. What is the use of molarity?

Students must be able to:

Calculate the molarity of a solution given the mass of the solute and the volume of the solution.

Calculate the concentration of ions present in a solution.

Calculate the number of moles of an ion in a solution given the volume of the solution.

Calculate the volume of solution that contains certain mass of solute, given the volume of the solution.

Determine the amount of solid that must be weight in order to prepare a certain volume of solution of a given concentration.

Calculate the volume of a solution of known concentration that is required to prepare a certain volume of a second solution of known concentration.

Calculate the molarity of a solution that is the result of a dilution process.

What is a standard solution? What is a stock solution?

What is dilution? Is it necessary to have a standard solution in order to make a dilution? Is it necessary to have a stock solution in order to make a dilution? Explain your reasoning for both questions.

A useful formula to make a dilution is M₁V₁ = M₂V₂, where M₁ is the molarity of the stock solution, V₁ is the volume of the stock solution, M₂ is the molarity of the desired solution, and V₂ is the volume of the desired solution. Notice that given any 3 quantities on the equation above, we can always solve for the fourth variable. This formula is very useful.

What is a chemical reaction? Define the parts of a chemical equation.

What are precipitation reactions?

What is a precipitate? How do we know when a precipitate is formed?

How do we know if a precipitate forms or not?

Students are expected to understand the solubility rules. Students must be able to apply the solubility rules when predicting the formation of a precipitate.

Students must be able to predict reaction products. How do we predict reactions products?

What is a complete ionic equation? What is the net ionic equation? What is the difference between a complete ionic equation and the net ionic equation?

Students must be able to:

Write formula equations for a given chemical reaction.

Write a complete ionic equation for a given chemical reaction.

Write a net ionic equation for a given chemical reaction.

Students must be able to understand and apply stoichiometry of precipitation reactions.

What is an acid-base reaction? What is an acid? What is a base? What is a neutralization reaction? Provide an example. What are the products of a neutralization reaction?

Students must be able to:

Calculate the volume of an acid of known concentration that is required to neutralize a given volume of base of known concentration.

Calculate stoichiometry for acid-base reactions.

Define acid-base titrations. Provide an example.

What is an indicator? How does an indicator is used in an acid-base reaction? Provide an example.

Define oxidation-reduction reactions. What is a redox reaction? What are the characteristics of these types of reactions? How do we balance oxidation-reduction reactions? Provide an example.

What are oxidation states? Students must be familiar with the rules to calculate oxidation states of an atom.

What is oxidation? What is reduction? How can we identify a specie that is being oxidized and a specie that is been reduced?

Answer 1

a) Is water the universal solvent? Why or why not? Is the water molecule polar? Why or why not?
Water is called the universal solvent because more substances dissolve in water than in any other solvent.
This is important to all the living thing on earth. The main reason for its solubility is the polarity of each water
molecule. The hydrogen side of each water (H2O) molecule carries a slight positive electric charge, while the oxygen side carries
a slight negative electric charge. This helps water dissociate ionic compounds into their positive
and negative ions. The positive part of an ionic compound is attracted to the oxygen side of water while the
negative portion of the compound is attracted to the hydrogen side of water.

b) Describe the process of hydration.
Ahydration reaction is a chemical reaction in which water combined to another chemical. For example: water is added
to an unsaturated substrate, which is usually an alkene or an alkyne. This reactin is used in the production of
ethanol, isopropanol, and 2-butanol.

c)Define solubility.
Solubility is a chemical property referring to the ability for a given substance, the solute, to dissolve in a solvent.
It is measured in terms of the maximum amount of solute dissolved in a solvent at equilibrium. The resulting solution
is called a saturated solution.
d) Do you expect sodium chloride to be soluble in water? Why or why not?
Yes. Sodium chloride is ionic compound. The sodium portion of the compounds carries a positive charge,
while the chlorine part carries a negative charge. The two ions are connected by an ionic bond.
When salt is mixed with water, the water molecules orient so that the negative-charge oxygen anions
faces the sodium ion, while the positive-charged hydrogen cations face the chloride ion.
Although ionic bonds are strong, the net effect of the polarity of all the water molecules is enough to pull
the sodium and chlorine atoms apart. Once the salt is pulled apart, its ions become evenly distributed,
forming a homogeneous solution.

e)Is ethanol, CH3CH2OH, soluble in water? Why or why not?

Ethanol is a small carbon skeleton molecule with a polar functional group that matches water.
Think of water as H-OH. Ethanol is CH3CH2-OH. The hydrogen bonding between the H of one of these molecules with
the lone pairs on an the atom of oxygen of the other molecule is quite strong. They are both polar substances.
If the carbon chain was increased quite a bit, the non-polar nature of the carbon skeleton would eventually prefer
weaker dispersion forces as the intermolecular force of attraction over the single OH group’s ability to hydrogen
bond with water.

f) Is hexane, CH3(CH2)4CH3, soluble in water? Why or why not?

Hexane = non-polar
Water = Polar, dipole-dipole interactions, and H-bonding

Think of "Like disolves Like". So, the hexane and water don't mix.