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Chem final review- Fall08

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									Chemistry
Final Exam (Fall)                                                                         Name___________________________
                                                       STUDY GUIDE
Particle Model
Use a particle model to differentiate between solids, liquids and gases
Compare and contrast the spacing of particles in solids, liquids and gases. Use observations of compression to support your
position.

The Water Molecule
Describe the oxygen and hydrogen atoms in a water molecule.
Include number of protons and electrons.
Which atom pulls harder on electrons? Explain your reasoning.
Describe the bond that holds together the hydrogen and oxygen atoms in a water molecule. How are the electrons shared? How
does this explain the polarity of the molecule- the oppositely-charged ends?
Support the claim of water to water particle attraction
Describe the dipole-dipole attraction (hydrogen bonding) that accounts for the observed water to water particle attraction

Changing Phases: ICE MELTS
When solid water (ice) melts to become a liquid, what happens to the molecules of water? What bonds were broken? What bonds
were not broken?
Enthalpy - Describe the direction of energy transfer. Is this reaction endothermic or exothermic? Did enthalpy (energy contents)
increase or decrease? Draw an energy graph to represent the change.
Entropy - What happened to the disorder (entropy)- increase or decrease? Explain.
When the process is reversed, (when the water freezes) how does the enthalpy and entropy change?

Changing phases: WATER BOILS
When liquid water boils to become a gas, what happens to the particles? Write an equation to show the change. What bonds were
broken? What bonds were not broken?
Enthalpy- Describe the direction of energy transfer. Is this reaction endothermic or exothermic? Did enthalpy (energy contents)
increase or decrease? Draw an energy graph to represent the change.
Entropy- What happened to the disorder (entropy)- increase or decrease? Explain.
When the process is reversed, (when the water condenses) how does the enthalpy and entropy change?
Write the equation for vaporization.

Water: Adding Heat Energy to Solid Water
To use the particle model to explain phase change (liquids and solids) and energy transfers
Calculate the total heat transferred from the hot water to the ice in the bag in Joules.
Use the equation q= mC∆T. Specific Heat (Cp) for water is 4.18J/g˚C.
Express calculations to the appropriate number of significant digits.
Precision vs. Accuracy
Significant figures
Define temperature.
        When the temperature increases, what happens to the speed and kinetic energy of the particles?
        The temperature of the hot water (the surroundings) outside the ice (the system) decreased. What does this tell
            you about the kinetic energy of the water molecules in the hot water? What does it tell you about the
            direction of the energy transfer?
        While the ice melts, the temperature of the ice remains at 0˚C. What does this indicate about the water
          molecules?
        Heat is the transfer of energy from hot to cold.
        Compare the particles of the hot and cold areas. Include motion and kinetic energy in you description.

Water: Adding Heat Energy to Liquid Water
To use the particle model to explain phase change (liquids and gases) and energy transfers.
         Draw a diagram of the distillation of water.
         Where is the water boiling? What is the temperature?
         Where is the water condensing? How does the temperature compare to the boiling location?
Before the water boils, what happens to the temperature of the liquid water as heat is added? How does the transfer of heat into the
flask from the surroundings affect the particles? Do the particles gain kinetic energy or potential energy? Justify your answer.
The temperature of the boiling water stays constant at 100˚C, even though heat is still being transferred into the flask. Are the
particles moving any faster as a result? Explain your thinking. How does the transfer of heat into the flask from the surroundings
affect the particles? Do the particles have more kinetic or potential energy as a result of the added heat? Justify your answer.


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After heating the boiling water, what is the gaseous product? What has happened to the water molecules? What bonds broke?
What bonds did not break? (Hint: Do you still have water molecules?)
Sketch the water molecules in the liquid to show the spacing of the particles.
Sketch the water molecules in the gas to show their spacing.
Label the force that acts between the molecules.
Label the force that acts between the atoms within the water molecules.
Label the particle arrangement with more potential energy and with less potential energy.
Include a label to show why they have more PE.
Enthalpy. Explain whether the boiling reaction is endothermic or exothermic. Explain in terms of energy transfer, systems and
surroundings. What happens to the energy content of the system? When is there more potential energy? Explain why. Construct
an energy graph to show the relative energy levels of the liquid and gaseous water and the energy change. Based upon the change
in enthalpy is this reaction favored to occur in this direction?
Entropy. Explain whether entropy increases or decreases in this reaction. Based upon the change in entropy, is this reaction
favored to occur in this direction?

Changing phases: WATER CONDENSES.
Write the equation for water condensing.
When the water condenses, what happens to the molecules of water? Compare the change at the particle level to the stretch and
release of a spring. Include potential energy and kinetic energy in your description.
The water condensed in the flask (the system), that was placed in an ice bath (the surroundings). Over time the ice outside the flask
(the surroundings), melted and the temperature of the melt water increased. What does this suggest about the energy transfer- from
the system out to surroundings or from surroundings into the system? Justify your answer.
In order to boil water, 2257 Joules (540 calories) of heat must be absorbed per gram of water. Is energy absorbed or released in the
condensation of 1 gram of water? Explain your reasoning. How much energy? Is condensation an endothermic or exothermic
process?
Based upon the change in entropy, is this reaction favored to occur in this direction? Explain.
Compare and contrast the freedom of movement of particles in solids, liquids and gases. Use your observations of pouring and
objects passing through it to support your position.

PHASE CHANGE DIAGRAM
Draw a phase change diagram to show the effect of temperature on water from a solid to gas- with temperature on the y-axis and
added heat on the x- axis. Label the heat of fusion, heat of vaporization, solid, liquid and gas.
       a. Explain the areas of the graph that show where adding heat leads to an increase in temperature.
                  How does the transfer of energy as heat affect the particles?
       b. Explain the areas of the graph that show where adding heat does not change the temperature.
                  Explain why the transfer of heat does not increase the temperature?
                  What is happening to the particles?

EVAPORATION. Describe evaporation at room temperature. Which particles tend to escape? Explain your thinking. What
happens to the temperature as a result?

BOILING VS EVAPORATION. Compare and contrast boiling and evaporation. Where do they occur in the water? At what
  temperature do they occur?

VAPOR PRESSURE EQUILIBRIUM occurs in closed container.
A reversible reaction in a closed system will eventually reach equilibrium.
         When the container is first closed, describe vaporization at the particle-level. Write an equation for this reaction. What
              happens to number of water molecules in the air above the liquid as vaporization continues?
         As the number of water molecules in the air above increases, describe the reverse reaction that is also occurring. Write an
              equation for this reverse reaction.
         As the number of water molecules in the air above the liquid increases,
                   What happens to the rate of the reverse reaction (condensation: gas --> liquid)?
                   What happens to the rate of the forward reaction (vaporization: liquid --> gas)?
         Eventually the forward reaction occurs at a rate equal to the rate of the reverse. Describe this state of equilibrium. Write
              a reversible equilibrium equation to show the equilibrium. What happens to the number of water molecules in the air
              above the liquid when the system is at equilibrium? How is this state related to the rates of the two reactions?
         If the system in a closed container at equilibrium is left undisturbed, it will remain at equilibrium. If the temperature
              changes the equilibrium will be disturbed. If the temperature of the liquid increases, what happens to the water
              molecules in the liquid? What will happen to the number of water molecules above the liquid? How is this related to
              the relative rates (Which reaction is temporarily faster?) How does this show that the system is no longer at
              equilibrium?


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         Are vapor pressure and temperature directly or inversely related? Explain why using your definition of temperature and
             vapor pressure.
         Boiling occurs when the vapor pressure of the liquid is equal to the external atmospheric pressure. The vapor pressure of
         the particles in the bubbles is equal to external pressure, thus bubbles form and maintain their shape until they rise to the
         surface. If the atmospheric pressure is lower (like at high altitudes), will the water boil at a lower or higher temperature?
         Explain your reasoning.

Water: Adding Electrical Energy to Liquid Water
Explain the decomposition and synthesis of water
Sketch an electrolysis set-up. Label the positive and negative terminals.
Identify the products. After the electrolysis of water do you have the same substance- water molecules?
Clearly support your answer with evidence from the lab.
Write a balanced equation to summarize the reaction.
Explain why this is a chemical reaction and the boiling of water is a physical change.
How is the electrolysis or decomposition of water observed in this part of the lab different from the boiling of water? What
happened to the water molecule in each reaction? What bond broke in each reaction?
Use a particle model to explain what happened to the molecule of water when electricity is added.
Describe the water molecule – the reactant.
               Describe the polar covalent bond and how the electrons are shared.
Describe the molecules in the products. Describe the nonpolar covalent bonds.
What bonds were broken and formed? What happened to the electrons?
This reaction was a decomposition or analysis reaction. Define a decomposition reaction.
Enthalpy Change associated with the Decomposition of Water-
Explain whether energy was transferred into or out of the system during the decomposition reaction. Describe observations
that support your interpretation about the direction of energy transfer.
Is the reaction endothermic or exothermic?
Do the products or reactants have a higher energy content- more potential energy (enthalpy)?
Bonds were broken in this chemical reaction. Does this process absorb or release energy? Will this be represented on the
graph as an increase or decrease in energy?
Bonds were also formed in this chemical reaction. Does this process absorb or release energy? Will this be represented on the
graph as an increase or decrease in energy?
Construct the energy graph to show the relative energy levels of the reactants and products and the energy change. Show the
breaking and forming of bonds. Label activation energy, activated complex, energy added to break bonds, energy released in
formation of bonds and the net energy of the reaction.
Describe the reaction in terms of the energy added to break bonds and the energy released in the formation of bonds. Compare
the energy added to the energy released.
Did enthalpy increase or decrease in the reaction? Is the change in enthalpy positive or negative?
Is the reaction favored based upon enthalpy?
Entropy Change associated with the Decomposition of Water-
Did entropy increase or decrease in the reaction? Explain your reasoning.
Is this reaction favored based upon entropy?
The reverse reaction is a synthesis reaction. Define synthesis. Write an equation for the synthesis of water.
Predict whether the synthesis of water will be endothermic or exothermic. Explain your prediction.

Collision Model and Rates of Reaction. Hydrogen and oxygen gas were both present in the test tube at room temperature, yet
no noticeable reaction occurred.
         Use collisions, activation energy (the energy required to break bonds), effective collisions, and temperature to explain
             why the reaction does not occur at a noticeable rate at room temperature, but does occur when a spark is added.
         When the spark is added the reaction was explosive. Was more energy added to break the bonds or released when the
             new bonds formed? Explain.

Intermolecular Forces of Attractions (IMF) and States of Matter. Water was liquid at room temperature, while hydrogen
and oxygen were gases at room temperature. Particle attractions (intermolecular forces- IMF) can be used to explain this.
        Describe and name the bond that holds together the hydrogen and oxygen atom in a water molecule. Does this lead to
            oppositely-charged ends?
        Describe and name the bond that holds together the hydrogen atoms in a molecule of hydrogen gas. Describe and
            name the bond that holds together the oxygen atoms in a molecule of oxygen gas. Does this lead to oppositely-
            charged ends?
        Use bonding and intermolecular forces to explain why water is a liquid and oxygen and hydrogen are gases at room
            temperature. Compare the IMF in water to that in hydrogen and oxygen gas.

Aqueous (Water) Solutions
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PART I. Adding Different Liquids to Water
Aqueous solutions are formed when substances (the solute) are dissolved in water (the solvent). Many chemical reactions occur in
solution.
MIXING DIFFERENT LIQUIDS
oil (simple hydrocarbon) and water
acetic acid (vinegar) and water
alcohol and water
acetic acid to oil and then alcohol to oil
hydrochloric acid- HCl to water
Hexane added to water and oil. Kerosene added to water and kerosene
Drag drops of alcohol, water and vinegar on wax paper
Demo- thin stream of water near a charged rod
     Use particle attractions ( a simplistic IPS model) to explain the mixing or lack of mixing of different liquids with water.
     Use density to explain the oil and water layers.
     Describe the evidence to support the statement, "Water molecules are strongly attracted to one another." List at least four
          pieces of evidence.
     Describe the evidence to support the statement, "Alcohol molecules are less attracted to each other than water molecules are to
          each other.”
     Use attractions and the definition of temperature to explain the greater evaporative cooling effect of alcohol compared to
          water.
     Use particle attractions to predict whether alcohol will have a greater or lesser vapor pressure than water. Explain your
          reasoning. Explain how this will result in lower boiling point for alcohol.
Draw an energy graph for the addition of HCl to water. Explain the temperature change. Is the reaction endothermic or
exothermic? Is energy transferred into or out of the system?
     Hydrochloric acid is an acid. What ion is present in acidic solutions?

ALKANES.
     Draw and name the first 8 simple hydrocarbons (alkanes)- from methane to octane. (Holt p 244)
     The electronegativity of carbon is 2.5. The electronegativity of hydrogen is 2.1. Use these electronegativities to name and
         describe the bond between carbon and hydrogen.
     Name and describe the attractions between alkane molecules.
     Draw the functional group on an alcohol hydrocarbon. Draw and name an organic alcohol. (p. 241)
     Draw the functional group on an acidic (carboxylic acid) hydrocarbon. Draw and name an organic acid. (p. 241)
     Rank the following in terms of their polarity: alcohol, oil and water. Explain.
     Compare the structure of a water molecule, alcohol molecule, and hexane molecules to explain how water molecules are
         attracted to alcohol molecules, but not at all attracted to hexane molecules.
     Describe what happens to alcohol molecules when the alcohol dissolves in water. Use random motion and attractions in your
         description. Identify and describe the attractions between alcohol molecules and water molecules.
     Use random motion and attractions to explain what happens when oil dissolves in kerosene. Explain why the oil did not
         dissolve in the water.
Explain the phrase “like dissolves like”. Give examples.
Hexane and methane are both hydrocarbons. Address both attractions and mass to explain why methane is gas and hexane is a
liquid.

Aqueous (Water) Solutions
PART 2. Adding Different Solids to Water
sodium chloride- NaCl              ammonium nitrate- NH4NO3        sugar or sucrose (C12H22O11)
sodium hydroxide- NaOH             aluminum- Al                    magnesium- Mg
copper- Cu                         zinc- Zn                        sulfur- S
sodium- Na- a demonstration
        Which solids tested are elements? Which are metals? Which are nonmetals?
        Which solids tested are compounds? Based upon the IPS model, which compounds are ionic and which are covalent?


CONDUCTIVITY
     Describe an electrical current.
     In order to conduct an electrical current, what two conditions of the particles must be met?

CONDUCTIVITY OF ELEMENTS
     Which elements conduct electricity? What other observed properties do these elements share?
     How is the element that does not conduct visibly different from the elements that conduct?


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        Describe how the solids can conduct electricity. Are the atoms free to move? Do the atoms have a charge? What
            charged particles are free to move?

CONDUCTIVITY OF COMPOUNDS
     What kind of compounds do not conduct electricity when dissolved in solution? What combination of elements is
         characteristic of these compounds?
     What kind of compounds conduct electricity when dissolved in solution? What combination of elements is characteristic
         of these compounds?
     Explain why these compounds conduct in solution, but not as solids. Think: Are there charged particles? Are they free to
         move? What kind of particles? What happens to them when it dissolves?
     Explain why the other compounds do not conduct? What kind of particles? What happens to these particles when the
         solid dissolves.

SODIUM CHLORIDE.
     Is sodium a metal or nonmetal? What happens to sodium’s electrons, when it becomes a more stable ion? What is the
          charge on the ion?
     Is chlorine a metal or nonmetal? What happens to chlorine’s electrons, when it becomes a more stable ion? What is the
          charge on the ion?
     Name and describe the bond that holds together solid sodium chloride.
     In order to conduct electricity charged particles must be free to move. Describe what happens to sodium chloride when it
          dissolves. What happens to the ions in solution that allows the solution to conduct electricity?
     Explain why the solid sodium chloride, NaCl (s), does not conduct electricity, but the solution, NaCl (aq), does.
     Describe the attractions of the ions in the solution. What was the sodium ion attracted to in the solid? What is the sodium
          ion now attracted to?
     Entropy - disorder. Explain when sodium chloride is more organized as a solid or in solution. Did the entropy increase or
          decrease when it dissolved?

SODIUM HYDROXIDE
   An ionic bond holds together sodium ions and hydroxide ions in solid sodium hydroxide.
       Describe the attractions between the ions in the solid. Name this bond. What must happen to this attraction when the
            sodium hydroxide is added to water. Draw a diagram of the solid sodium hydroxide.
       What new attractions are formed in solution? Describe and draw the solution of sodium hydroxide.
       Describe the reaction in terms of energy added to break bonds and energy released when bonds form. Was this reaction
            endothermic or exothermic? Support with your observations. Make an inference about the energy to break compared
            to the energy released in formation.
       Construct an energy graph to show the relative energy levels of solid sodium hydroxide and aqueous sodium hydroxide. Is
            this reaction favored to occur based upon the change in enthalpy? Explain.
       Is this reaction favored based upon the change in entropy? Explain your reasoning.
       Sodium hydroxide is a base. What ion is present in basic solutions?
                                                                       +                      -
AMMONIUM NITRATE An ionic bond holds ammonium ions- NH4 and nitrate ions- NO3 together in solid ammonium
nitrate.
         Ammonium and nitrate are both polyatomic ions. Define a polyatomic ion.
         Describe what must happen to the ions and the bonds when the ammonium nitrate is added to water. What new bonds are
              formed?
         Describe the reaction in terms of energy to break the original bonds and energy released in the formation of new bonds.
              Was this reaction endothermic or exothermic? Support with your observations. Make an inference about the energy
              added to break compared to the energy released in formation.
         Construct an energy graph to show the relative energy levels of solid ammonium nitrate and aqueous ammonium nitrate.
              Is the reaction favored based upon enthalpy?
         Is this reaction favored based upon entropy? Explain your reasoning.
         This reaction did occur at room temperature. Which factor favored the reaction? Which factor did not favor the reaction?
              Which favor must have made a bigger difference?

METALS. Metals conduct electricity. Metals have a loose-hold on their electrons. The electrons are shared by all the atoms as a
loose sea of electrons- a metallic bond.
         a. Describe a metallic bond. What charged particles are free to move in the solid metal? How does this relate to
              conductivity?
         b. The solid metals are composed of atoms. Locate the five metals on the periodic table. For each metal- answer the
              following questions in an organized table.
              • What is the atomic number?
              • How many protons and electrons in the neutral atom?
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             • What column is it located in? What row?
             • What is the atomic mass?
             • What is the mass of one mole? How many atoms in the one mole?
         c. Which metals reacted in water? What is your evidence? Which metal must be the least stable? Explain your
             reasoning.
         d. Which metals did not react in water? What is your evidence? Are these metals stable or unstable? Explain your
             reasoning.
         e. Propose an explanation for the difference in the behavior of the metals.

COLLISION MODEL. Use the collision model to explain how increasing the temperature of the water would increase the rate of
reaction when magnesium is added to water. Remember: In order to react the particles must hit with enough force to break bonds.

CONCENTRATION CALCULATIONS
     What is a mole? What is it used to count?
     Draw the “mole map.” How is mass converted to moles & moles to mass? How are moles converted to number of
         particles? How can you find the mass if given # molecules?
     What is the difference between moles and molarity (M)? How is molarity calculated?
     What is Ksp? What information is needed to calculate Ksp?
     Find the mass per mole of the following compounds:
                        sodium chloride, sodium hydroxide, ammonium nitrate
     Find the concentration of the solution in moles/ liter
              If 0.5 grams of each solid was added to 15 mL of water.
              If 5 grams of each solid were dissolved in 50 mL of water.
     Find the Ksp for NaCl if 2.1 g NaCl can dissolve in 10 mL of water. If 1.2 g MgSO 4 dissolves in 10 ml of water, which is
         more soluble: NaCl or MgSO4? Does a low Ksp represent high or low solubility?

Different reactions are used to allow you to show your understanding of the chemistry concepts of the first semester. Write the
balanced equations for each reaction, including the symbols for the phases. Conceptual questions and calculations follow each
reaction. Answers should be detailed to completely show your understanding.
1. Write the balanced equation for the combustion of propane.
                            C3H8 - a simple hydrocarbon
         (a) How many moles of carbon dioxide gas will be produced when 135.0 grams of propane are burned?
         (b) The combustion of propane and other hydrocarbons are exothermic. What does this mean? Represent the energy
         relationships on a graph. Label the products, reactants, activation energy and net energy released or added. How does the
         potential energy of the products and reactants compare?
         (c) Why is the spark necessary to start the reaction? What must happen to the molecules in order for a reaction to occur?
         (d) Compare potential energy and kinetic energy. How does the potential energy of the reactants compare with the
         products? When was kinetic energy involved? Discuss both the motion and position of the particles.

2. Write the balanced equation for the electrolysis of water (decomposition)
        (a) Was energy an input or output ? When do the molecules have more potential energy? What was changed in order to
        change the potential energy?
        (b) Water is liquid at room temperature, while both hydrogen and oxygen are gases at room temperature. Use particle
        attractions to explain why. Discuss the bonds that hold together the hydrogen and oxygen molecule and the bonds that
        hold together the water.
        (c) Describe the spacing and movement of particles in solids, liquids, and gases.
        (d) How many moles of oxygen will be produced from the decomposition of 1.00 gram of water?
        (e) Use the density of water to find the volume of 1.00 gram of water.
        (f) At STP, what is the volume of the moles of oxygen produced in the above reaction.

DOUBLE REPLACEMENT REACTIONS
For a reaction such as: “mercury (I) nitrate + sodium carbonate ” be able to:
         (a) Write the predicted products in words.
         (b) Write the formulas.
         (c) Identify the insoluble precipitate (using a solubility rules chart)
         (d) Balance the equations.
         (e) Write the total ionic equation
         (f) Write the net ionic equation

SINGLE REPLACEMENT REACTIONS
      (a) Identify whether a reaction will take place (using an activity series chart)
      (b) Write half-reactions to show oxidation and reduction in single replacement reactions
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