Download Unit 8 Note Packet

Honors Chemistry
Unit 8
(2015-2016)
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Chemical Reaction/Equations
Balancing
Word Equations
Translating to sentences
Energy Changes for Chemical & Physical Changes
We are learning to:
1. Chemical equations (terms, symbols, translating)
2. Balance a chemical equation based upon the law of conservation of matter.
3. Analyze or draw a graph for the energy change of a chemical reaction.
4. Calculate the heat of solution for a given compound.
We are looking for:
1a. Given the word equation/sentence, translate it into a formula chemical equation and vice versa.
1b. Use the proper symbols in a chemical equation such as (s), (l), (g), (aq).
2a. Balance a chemical equation by using coefficients to make sure that each type of atom has the
same amount on the reactant and product side of the chemical equation.
3a. Define enthalpy.
3b. Given an energy graph/diagram for a reaction, determine the activation energy and the energy of
the activated complex.
3c. Draw and label an energy diagram for a reaction.
3d. Explain the concept of activation energy and activated and catalyst.
3e. Classify changes in energy as exothermic or endothermic.
4. Given data, calculate the energy gained or lost per mole when a compound dissolves (KJ/mole).
1
Name _____________________________________________________
The information on the left side of the arrow is correct.
What's wrong on the right hand side of the arrow?
1. Trisilicon pentoxide →
2. FeSO4 →
Iron (II) sulfide
3. Cr(NO3)3 →
4. P2Cl5 →
S3O5
Correct =
Correct =
Chromium nitrate
Correct =
diphosphide pentoxide
Correct =
5. Copper (I) oxide
→
CuO2
Correct =
6. Dinitrogen tetrasulfide → (NO3)2 (SO4)
Correct =
7.
Barium Phosphate →
Correct =
8.
CaBr2 →
9.
SO →
10.
Be3(PO4)2
Calcium (II) Bromide
Sulfur oxide
SnO →
Correct =
Tin Oxide
11. Hexanitrogen dichloride →
12. NiC →
13.
Nickel (II) Carbide
Zinc Fluoride →
Correct =
ZnFl2
Correct =
N2Cl6
Correct =
Correct =
Correct =
2
Refresher on Ionic Naming
(metal and nonmetal)
I II III IV V VI VII VIII IX X
Formula to name:
1. Convert metal symbol to a name using the periodic table
If it is Sn or Pb or it is a D-Block metal (except Scandium family (3+) , Ag (1+) Zn (2+),
Cd (2+))
It will need a roman numeral
To get the roman numeral, uncriss cross the subscripts and make them
superscripts.
PbBr2
Pb Br2
Pb2+ Br(Bromine is 1- from the periodic table)
Check the negative charge…is it correct?? If yes, then so is the metal. Convert
the number the metal has to a roman numeral and put it after the metal’s name.
so in the above example the metal would be lead (II), which makes the
full name lead (II) bromide.
Another example:
SnSO4
SO4 is a polyatomic so it looks like Sn is + and SO4 is – since they are in a one to one ratio
BUT from the the charge of SO4 is 2- which means Sn must be 2+ ,tin (II), which makes
the full name tin (II) sulfate.
2. Convert the anion to a name
a. If it is a single element, it is named after an element on the periodic table.
Make sure the name ends with – IDE
(IDE—I’d check the table)
b. If it is a polyatomic ion , name the polyatomic ion. Remember though,
if it matches the –ate ion exactly, it will end in ATE
If it has one more oxygen then changes to
If it has one less oxygen then changes to
If it has 2 less oxygens then changes to
PER….…ATE
---ITE
HYPO……ITE
3
Ionic Name to formula:
1. Convert the metal to its symbol
You need its charge (it will be a positive superscript)
If it has a roman numeral – that is the charge – it is positive
If it doesn’t have a roman numeral you have to get it from the periodic table
2. Convert the nonmetal to its symbol (it will be a negative superscript)
If it is a single element from the periodic table – use the oxidation pattern
If it is a polyatomic, use the charge for that ion.
3. To get the balanced formula you must criss cross
If the subscripts can be simplified…you must do that!
Ex: Iron (III) bromate
= Fe3+ BrO3- =
Fe3+ BrO3-
=
Fe(BrO3)3
_______________________________________________________________________
Refresher on Covalent Naming
(2 nonmetals)
mono di tri tetra penta hexa hepta octa nona deca
Formula to Name:
1. Name the first nonmetal as it appears on the periodic table.
Put a prefix counter in front of it to tell how many of them there are (see above).
If there is only one…do not use the term mono – just use the element name
2. Name the second nonmetal
a. Name the element from the periodic table and change the ending to -IDE
Put a prefix counter in front of it to tell how many of them there are.
If there is only one – you must use the term mono !
Name to Formula:
1. Turn the first element name into a symbol
a. If there is a prefix in front of it - convert it into a subscript after the element symbol
b. If there is not a prefix, assume there is one of that element
2. Turn the second element into a symbol
a. Take the prefix in front of it and convert it into a subscript after the element symbol
4
Refresher on Acids Naming
(H + nonmetal or polyatomic ion)
Binary Acids: (H + a nonmetal element)
1. Start the name with hydro2. Name the nonmetal and change the ending to –ic (sulfur becomes sulfuric; phosphorus
becomes phosphoric).
3. Put the word acid at the end.
Ex) HCl = hydrochloric acid
H2S = hydrosulfuric acid
Ternary or Oxy Acids: (H + a polyatomic ion)
1. Name the polyatomic ion present.
2. If the ion ends in –ate (pernitrate or nitrate), change the ending to –ic.
If the ion ends in –ite (nitrite or hyponitrite), change the ending to –ous.
3. Put the word acid at the end.
Ex) H2CO3 = carbonic acid
H2CO4 = percarbonic acid
H2CO2 = carbonous acid
H2CO = hypocarbonous acid
**Reminder, the amount of hydrogen used in the formula is equivalent to the charge value of the
nonmetal or polyatomic ion.***
___________________________________________________________________________________
Chemical vs. Physical Changes
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8
9
10
Name_________________________________________________
Balancing Practice Problems
1.
___Na + ___MgF2
→
___NaF + ___Mg
2.
___Mg + ___HCl
→
___MgCl2 + ___H2
3.
___Cl2 + ___KI
→
___KCl + ___I2
4.
___NaCl
5.
___Al4C3 + ___ H2O  ___CH4 + ___ Al(OH)3
6.
___Na + ___O2
7.
___Na + ___HCl
→
___Na + ___Cl2
→
→
___Na2O
___H2 + ___NaCl
11
8.
___Ca3(PO4)2 + ___ H2SO4  ___CaSO4 + ___H3PO4
9.
___K + ___Cl2
→
___KCl
10.
___CO2 + ___H2O 
___C3H8 + ___O2
11.
___C7H6O2 + ___O2 
___CO2 + ___H2O
12.
_____ NH3 + ____ O2  ____ NO2
13.
_____P4O10
+ ____H2O
+ ____HNO3  ____H3PO4
+ ____ N2O5
12
Name __________________________________________________
Balance each of the following equations:
1. ___ Zn + ___HCl  ___ ZnCl2 + ___ H2
2. ___Sb + ___ O2  ___ Sb4O6
3. ___H3AsO4  ___ As2O5 + ___ H2O
4. ___N2O5 + ___H2O  ___HNO3
5. ___Fe2O3 + ___ C  ___CO + ___ Fe
6. ___Si2H3 + ___ O2  ___ SiO2 + ___ H2O
7. ___Na2O2 + ___ H2O  ___NaOH + ___O2
13
8.
___PCl5 + ___ H2O  ___H3PO4 + ___ HCl
9. ___NH4NO3  ___ N2O + ___ H2O
10. ___BaCl2 + ___Al2(SO4)3  ___BaSO4 + ___AlCl3
11. ___C6H6 + ___ O2  ___CO2 + ___ H2O
12. ___As + ___NaOH  ___Na3AsO3 + ___ H2
13.. ____K2Cr2O7 + ___HCl  ___ KCl
+ ____CrCl3 + ____ H2O + ____ Cl2
14. ___Ca10F2(PO4)6 + ___H2SO4  ___Ca(H2PO4)2 + ___CaSO4 + ___HF
14
Name_____________________________________________________
Converting Word Equations into Balanced Chemical Equations
(see p. 3-5 for a refresher on names & formulas)
1. Aluminum Bromide + Chlorine yields Aluminum Chloride + Bromine
2. Zinc + Lead (II) Nitrate yields Zinc Nitrate + Lead
3. Hydrogen + Carbon Monoxide yields dihydrogen monoxide + Carbon
4. Sodium + Hydrofluoric acid yields Sodium Fluoride + Hydrogen
5. Copper + sulfuric acid yields Copper (II) Sulfate + dihydrogen monoxide + Sulfur Dioxide
6. Potassium Carbonate + Calcium Chloride yields Calcium Carbonate + Potassium Chloride
15
7. Iron (III) Oxide + Carbon Monoxide yields Iron + Carbon Dioxide
8. Aluminum Oxide + Dihydrogen Monoxide yields Aluminum Hydroxide
9. Hydrochloric acid + Calcium Carbonate yields Calcium Chloride + Dihydrogen Monoxide
+ Carbon Dioxide
10. Strontium Iodide + Lead(II) Phosphate yields Strontium Phosphate + Lead (II) Iodide
11. Magnesium + Nitrogen yields Magnesium Nitride
12. Butane (C4H10) + Oxygen yields Carbon Dioxide + Dihydrogen Monoxide
16
On a separate sheet of paper, translate the following sentences into a balanced
chemical reaction:
1) Solid sulfur trioxide and water combine to make sulfuric acid.
2) Aqueous lead (II) nitrate and aqueous sodium iodide react to make solid lead(II) iodide and
aqueous sodium nitrate.
3) Aqueous calcium fluoride and sulfuric acid react to form solid calcium sulfate and
hydrofluoric acid.
4) Solid calcium carbonate will come apart when heated to produce solid calcium oxide and
carbon dioxide.
5) Aqueous aluminum sulfate and aqueous magnesium hydroxide will react to form solid
aluminum hydroxide and aqueous magnesium sulfate.
6) Copper metal and aqueous silver nitrate react to form silver metal and aqueous copper (II)
nitrate.
7) Gaseous propane (C3H8) will react with oxygen gas when heated to produce carbon dioxide
gas and gaseous dihydrogen monoxide.
_______________________________________________________________
On a separate sheet of paper, write a balanced chemical reaction for each of the reactions
described below (include all possible symbols):
1) Barium metal and aqueous hydrochloric acid react to produce solid barium chloride and
hydrogen gas.
2) Using heat, aqueous nitric acid reacts with solid magnesium hydroxide to make aqueous
magnesium nitrate and liquid dihydrogen monoxide.
3) Solid Aluminum carbide reacts with dihydrogen monoxide in the liquid form at 450.0 oC to
yield methane gas, (CH4), and solid aluminum hydroxide.
4) Lead (II) acetate in the solid form and aqueous hydrosulfuric acid react to form solid Lead
(II) sulfide and liquid acetic acid.
_______________________________________________________________________
On a separate sheet of paper, write out these reactions in word form
and
sentence
form:
1. H2 (g) + Cl2 (g)  2HCl (aq)
2. 2Al (s) + Fe2O3 (aq) 
3. 8Pb (s) + S8 (s)

Al2O3 (aq) + 2Fe (s)
8PbS (s)
550 oC
4. Pb(NO4)2 (aq) + FeCl2 (aq)

PbCl2 (s) + Fe(NO4)2 (aq)
17
Balancing Worksheet Extra Practice
Please note that several of these equations are already balanced as written. There are 50 problems in two columns.
1.
2.
3.
4.
5.
6.
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8.
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10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
H2 + O2 ---> H2O
S8 + O2 ---> SO3
HgO ---> Hg + O2
Zn + HCl ---> ZnCl2 + H2
Na + H2O ---> NaOH + H2
C10H16 + Cl2 ---> C + HCl
Si2H3
+
O2 --->
SiO2
+
H2O
Fe + O2 ---> Fe2O3
C7H6O2 + O2 ---> CO2 + H2O
FeS2 + O2 ---> Fe2O3 + SO2
Fe2O3 + H2 --->
Fe
+
H2O
K
+
Br2 --->
KBr
C2H2
+
O2 --->
CO2
+
H2O
H2O2
--->
H 2O
+
O2
C7H16
+
O2
--->
CO2
+
H2O
SiO2
+
HF --->
SiF4
+
H2O
KClO3
--->
KCl
+
O2
KClO3
--->
KClO4
+
KCl
P4O10
+
H2O
--->
H3PO4
Sb
+
O2
--->
Sb4O6
C3H8
+
O2
--->
CO2
+
H2O
Fe2O3
+
CO
--->
Fe
+
CO2
PCl5
+
H2O
--->
HCl
+
H3PO4
H2S
+
Cl2
--->
S8
+
HCl
Fe
+
H2O
--->
Fe3O4
+
H2
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
N2
+
H2 --->
NH3
N2
+
O2 --->
N2O
CO2
+
H2O --->
C6H12O6
+
O2
SiCl4
+
H2O --->
H4SiO4 +
HCl
H3PO4 --->
H4P2O7
+
H2O
CO2
+
NH3 --->
OC(NH2)2 +
H 2O
Al(OH)3 + H2SO4 --> Al2(SO4)3 + H2O
Fe2(SO4)3 + KOH ---> K2SO4 + Fe(OH)3
H2SO4 + HI
---> H2S + I2
+
H 2O
Al
+
FeO
--->
Al2O3
+
Fe
Na2CO3 +HCl---> NaCl + H2O
+
CO2
P4
+
O2
--->
P2O5
38. K2O
+
H2O
--->
KOH
Al
+
O2
--->
Al2O3
Na2O2
+
H2O
--->
NaOH
+
O2
C
+
H2O
--->
CO
+
H2
H3AsO4
--->
As2O5
+
H2O
Al2(SO4)3 +Ca(OH)2---> Al(OH)3+ CaSO4
FeCl3 + NH4OH ---> Fe(OH)3 + NH4Cl
Ca3(PO4)2 +6SiO2 -->
P4O10 + CaSiO3
N2O5
+
H2O
--->
HNO3
Al
+
HCl
--->
AlCl3
+
H2
H3BO3
--->
H4B6O11
+
H2O
Mg
+
N2
--->
Mg3N2
NaOH + Cl2 ---> NaCl + NaClO + H2O
Answers
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
2, 1 ---> 2
1, 12 ---> 8
2 ---> 2, 1
1, 2 ---> 1, 1
2, 2 ---> 2, 1
1, 8 ---> 10, 16
4, 11 --->
8, 6
4, 3 ---> 2
2, 15 ---> 14, 6
4, 11 ---> 2, 8
1, 3 --->
2, 3
2, 1 --->
2
2, 5 --->
4, 2
2 --->
2, 1
1, 11 ---> 7, 8
1, 4 --->
1, 2
2 ---> 2, 3
4 --->
3, 1
1, 6
---> 4
4, 3
--->
1
1, 5
---> 3, 4
1, 3
---> 2, 3
1, 4
--->
5, 1
8, 8
--->
1, 16
3, 4
--->
1, 4
26.
27.
28.
29.
30.
31.
1,
2,
6,
1,
2
1,
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
1,
1,
2,
1,
1,
1,
4,
2,
1,
2
1,
1,
2,
1,
2,
6
3,
2,
3 ---> 2
1 ---> 2
6 --->
1, 6
4 --->
1, 4
--->
1, 1
2 --->
1, 1
32. 2, 3 ---> 1, 6
6 ---> 3, 2
8
--->
1, 4, 4
3 --->
1, 3
2 ---> 2, 1, 1
5
--->
2
1
---> 2
3
---> 2
2
---> 4, 1
1
--->
1, 1
--->
1, 3
3 --> 2, 3
3
--->
1, 3
6 ---> 1, 6
1
---> 2
6
---> 2, 3
--->
1, 7
1
--->
1
1
--->
1, 1, 1
18
Enthalpy and Energy Diagrams
Objectives:



Define enthalpy
Draw and label an energy diagram
Explain the concept of activation energy and activated complex
So far we’ve talked a lot about heat.



Heat is the change in energy due to a temperature difference.
Heat can be used to measure the energy in something
Heat moves from areas of hot to areas of cold.
A change in energy can also be described as a change in enthalpy when the system is at constant pressure
(open to the atmosphere = constant pressure)
Enthalpy: a measure of the energy content of a substance. This includes kinetic and potential. (It also includes
pressure-volume energy but we will ignore this in general chemistry).
Since we will always be dealing with constant pressure systems in chemistry (until we get to the gas laws unit), we
can say
q = H
Just like heat



H > 0 = Endothermic
H < 0 = Exothermic
Units: Joules, J
A visual for the change in energy of a reaction:
Activated
Reactants
Energy
Products
Reaction Coordinate
The diagram above shows that



Reactants are at a higher energy state than the products
The reaction is exothermic
An in-between compound (activated complex), is formed
19
Reaction Coordinate: a step in the process. Reactants have to “morph” into the products.
Activation Energy
Energy
H < 0
Reaction Coordinate
The diagram above shows that



The change in energy between reactants and products is the change in enthalpy
The reaction is exothermic
The reaction requires some energy before it will start, Activation Energy: Ea
Example of Activation Energy:
1.
2.
3.
4.
Candles don’t burn until you ignite them
Matches don’t light until you use some of your own energy as you strike them
The food didn’t burn until it was lit
The Nitrogen triiodide (remember explosion video) doesn’t explode until it was tickled
Analogy: Old Love, New Love
Reactants are like you and an old boyfriend/girlfriend…content until you break up. You are in a state of
agitation…activated complex…until you meet and bond with your new boy/girl and you are happy…at a low
energy state….a new product has been formed.
If you are happier than in previous relationship = exothermic
Happier in previous relationship = endothermic
What would an endothermic reaction look like graphically?
Activation
Energy
H
Reactants
Reaction
20
Name:__________________________________
1. From the diagram below match the letter to the appropriate term.
activation energy of forward reaction _____
products _____
activation energy of reverse reaction _____
reactants _____
activated complex _____
ΔH of reaction _____
Enthalpy (H) of products (energy) _____
Enthalpy (H) of reactants (energy) _____
Enthalpy (H) of activated complex (energy) _____
Referring to the diagram answer the following questions:
2. What is the ΔH of reaction of the forward reaction?
3. Is this reaction endothermic or exothermic?
4. What is the ΔH of the reverse reaction?
5. Is this reaction endothermic or exothermic?
6. What is the enthalpy of the activated complex?
21
Is the reaction above exothermic or endothermic? Explain.
How could you lower the activation energy for the above reaction?
22
HEAT OF SOLUTION
Reminder – Goggles must be worn at all times in the lab
PRE-LAB DISCUSSION:
When salts are dissolved in water, there is often a temperature change associated with the process. Some salts dissolve,
releasing heat in the process. Others dissolve while absorbing heat. As you may remember, processes that proceed with a
release of heat energy are called “exothermic” processes, while those that absorb heat are called “endothermic” processes.
Because energy is released to the surroundings in an exothermic process, the heat of solution would be given a negative value
because the energy of the system is decreasing.
NaOH(s)  Na+(aq) + OH-(aq)
ΔHsolution = - 44.51 kJ/mol
Because energy is absorbed from the surroundings in endothermic processes, the heat of solution would be given a positive
value because the energy of the system is increasing.
KNO3(s)  K+(aq) + NO3-(aq)
ΔHsolution = + 34.89 kJ/mol
In this experiment you will start with a known mass of calcium chloride, ammonium chloride, and a known volume of water. You
will determine the magnitude of the temperature change associated with the dissolving process, and use the masses of the
solute and solvent, the temperature change (called ΔT), and the known heat capacity (specific heat) of water, 4.184 J/(g⋅ °C),
to calculate the heat of solution for the 2 different compounds.
PURPOSE:
To apply the concepts of specific heat and temperature change in the experimental determination of the heat of solution of
two soluble salts, calcium chloride and ammonium chloride.
PROCEDURE:
1. Obtain a Styrofoam cup “calorimeter”. Measure about 40.0 mL of distilled water. Determine the mass of water used and
record this mass below in the observations. Place the water into the calorimeter.
2. Weigh out close to 1.00 grams of calcium chloride. Record the exact mass used.
3. Record the initial temperature of the water in the calorimeter.
4. Add the calcium chloride to the water in the calorimeter, all at once, and begin stirring the solution to dissolve the salt as
rapidly as possible. Stir by swirling the cup with your hand. DO NOT use a glass stir rod, as it will effect your results.
Watch out for the fragile thermometer! Record the new temperature achieved during the dissolving of the salt.
5. Cleanup: Rinse the solution down the sink with LOTS of water. Rinse the Styrofoam cup, and return it to the side counter.
DO NOT throw the Styrofoam cup away – we re-use them. Rinse the thermometer and return it to your lab drawer.
6. Repeat the procedure for ammonium chloride.
RESULTS
Observations and Data:
1. Mass calcium chloride used ________________g
2. Mass of water used ________________g
3. Initial temperature (T1) ________________°C
4. Final temperature (T2) ________________°C
5. Δ temperature ______________________ °C
23
1. Mass ammonium chloride used ________________g
2. Mass of water used ________________g
3. Initial temperature (T1) ________________°C
4. Final temperature (T2) ________________°C
5. Δ temperature ______________________ °C
Calculations: Show your work on a separate sheet of paper!
1. Calculate the energy change for the water as the calcium chloride or ammonium chloride dissolved. In order to do this,
we must assume that the solution has the same specific heat, c , as pure water [ 4.184 J/(g°C) ]. Express your final
answer in kilojoules, kJ!
q = m x c x ΔT
2. Calculate the number of moles of each salt used. (Moles are a unit of measure). Divide the number of grams you used for
each salt by the molar mass of each salt. The molar mass of calcium chloride is 110.98g/mol and the molar mass of
ammonium chloride is 53.49g/mol.
3. The energy change experienced by the water is caused by the energy change experienced by the salt as it dissolved.
Therefore, because of the law of conservation of energy, qwater = q”salt” . The heat of solution is calculated by dividing the
qsalt (in kJ) by the moles of salt dissolved. This is the heat of solution, expressed in kJ/mol of solute.
ΔHsolution = qsalt / mole of salt
4. Using the accepted value of the heat of solution of calcium chloride and the heat of solution of ammonium chloride,
calculate your percent error for each.
24
Energy/Enthalpy Diagrams
Use the following graph to answer the questions below.
1.
2.
3.
4.
5.
6.
7.
Name:__________________________________
Is the overall reaction (forward directions) exothermic or endothermic?___________________________
What is the activation energy for the forward reaction?_______________________
What is the activation energy for the reverse reaction?_______________________
What is the ΔH for the forward reaction?________________________________
What is the ΔH for the reverse reaction?________________________________
Is the reverse reaction exothermic or endothermic?_______________________
Which do you think would be faster, the forward reaction or the reverse reaction? ___________Why?
8. If a catalyst is used with this reaction, it can lower the activation energy by 20kJ. Use a dashed line on the graph
above to illustrate the progress of the reaction using a catalyst.
9. Label the following on the above graph: ΔH, the activation energy for the forward reaction (Ea) and the activation
energy for the reverse reaction Ea’.
10. What is the meaning of activation energy?
Draw an energy diagram using the following information:
The potential energy of the reactants is 50kJ.
The potential energy of the products is 15kJ.
The activation energy is 30kJ.
25