Download Unit 5 Spiraling

Chemistry Unit 5- Essential Knowledge
Unit 5 Problem Sets
(Answers for all problems, additional practice worksheets and a practice test are all eventually posted
on Blackboard)
Instructions: Do Problems as Assigned. They must be done on a separate sheet of paper in PENCIL. Your full
name (first and last), the date, and your class period must be in the upper right corner of your paper. Answers to
assigned problems must be legibly printed (no cursive). Typing is only permitted with special permission.
SHOWING YOUR WORK IS REQUIRED FOR ALL MATH PROBLEMS!!!!!!!!
At the end of every problem set you must write in ink the honor pledge: “On my honor as a W-L student, I have
neither given nor received aid on this assignment.” And sign your name.
Failure to follow this procedure will result in your paper being returned to you with no credit given.
Topic 1:
Elements and the
Periodic Table
Going down a group on the Periodic Table, each element has one more principal energy level filled with
electrons than the element above it, so the outer electrons are farther away from the nucleus. This means the
size of the atoms increases going down a group. Therefore the atomic radius increases going down a group.
Going from left to right across a period of the Periodic Table the valence electrons are all in the same principal
energy level, but the number of protons in the nucleus increases from one element to the next. This means that
the nucleus becomes more positively charged and attracts the electrons more strongly. Therefore, the atomic
radius decreases going from left to right across a period.
Problem Set 1.5
Topic 2:
Compounds and
Bonding
Circle the Atom that has the biggest radius?
1. F or Cl Why? _________________________
2. Li or F Why? ________________________
3. Si or Cl Why? _________________________
4. K or Ca Why? _________________________
5. O or B? Why? __________________________
6) Which element has the smallest radius?
a) Oxygen (O)
b) Carbon (C)
c) Tin (Sn)
d)Tellurium (Te)
Explain:
7) The radius of elements decreases going from left to right across a period on the periodic table because:
a) The principle quantum number of the outermost electrons increases
b) There are more neutrons in the nucleus
c) There are more electrons in the electron cloud
d) The nucleus attracts the electrons more strongly
Explain:
8) What is the trend in atomic radii on the periodic table?
a)Increase left to right, Increase top to bottom
b)Decrease left to right, Increase top to bottom
c)Increase left to right, decrease top to bottom
d)Decrease left to right, decrease top to bottom
Explain:
Electron dot diagrams for an element show the number of valence electrons for that element.
The Lewis dot diagram for a covalent compound shows how the atoms in a molecule share electrons to gain
a filled valence level. A filled valence level is called an octet. Lewis dot diagrams for most elements
(except: Hydrogen) generally follow the octet rule. Each shared pair of electrons in a Lewis diagram
represents a single covalent bond.
A covalent molecule can also be represented by a structural formula in which each covalent bond is shown
as a line joining two atoms. In other words, a line in a structural formula represents two electrons ( a
pair) shared by two elements.
Problem Set 2.5
1. Give the Formula, # of valence electrons, Dot picture, and Structural Formula for the following molecules.
CCl4
C2H6
CO2
O2
N2
HCN
NH4+
SO42PO432. Write the names of the following chemical compounds:
a) BBr3 b)CaSO4
c)C2Br6
d)Cr(CO3)3
e)Ag3P
f)IO2
g)VO2
h)PbS
i)CH4
j)N2O3
3. Write the formulas of the following chemical compounds:
a)tetraphosphorus triselenide
b)potassium hydroxide
c)iron (II) phosphide
d)disilicon hexabromide
e)titanium (IV) nitrate
f)diselenium diiodide
g)copper (I) phosphate
h)magnesium carbonate
i)tetrasulfur dinitride
j)ammonium oxide
Topic 3:
Kinetic Theory
In chemical reactions bonds are broken and new bonds are formed. The energy absorbed in breaking the
bonds is never exactly equal to the energy released when the new bonds are formed. Therefore, all reactions
are accompanied by a change in potential energy that can be measured and is represented by the symbol
 H.
An energy level diagram can also be used to represent the energy change during a chemical reaction.
For Exothermic reactions (H), the energy required to break the bonds of the reactants is less than the
energy released in making the bonds of the products.
For Endothermic reactions (+H), the energy required to break the bonds of the reactants is greater than
the energy released in making the bonds of the products.
Problem Set 3.5
Topic 4:
The Mole and
Stoichiometry
Read pages 541-546 Do Intepreting Graphs a, b, and c on 543, Intepreeting Graphs a, b, and c on 547 and
Answer Questions 2, 4, 5 in Section Assessment on 547
Because matter cannot be created or destroyed, the total mass of the products is equal to the total mass of
the reactants in a chemical reaction. This is why we balance chemical equations to insure that there are the
same total numbers of each element on each side. If the number of atoms are the same then the total mass of
the reactants = the total mass of the products.
The theoretical yield (mass of the product) can be predicted from the mass of a reactant. Molar masses
from the periodic table and mole ratios from the balanced equation can be used to calculate the mass of a
reactant or product.
Problem Set 4.5
Topic 5:
Chemical Reactions
1. Use the balanced chemical reaction for the combustion of propane, C3H8
C3H8 + 5 O2  3 CO2 + 4 H2O
Write the mole ratios based on the balanced chemical reaction.
____________C3H8 = __________ O2
____________C3H8 = __________ CO2
____________C3H8 = __________ H2O
____________O2 = ___________ C3H8
____________O2 = ___________ CO2
____________O2 = ___________ H2O
a. How many moles of carbon dioxide will be produced if 20 moles of propane react?
b. How many moles of oxygen react with 20 moles of propane?
c. If 8.50 moles of water is produced by this reaction, how many moles of oxygen reacted?
2. Laughing gas, N2O can be turned into smog NO2 by heating the laughing gas in the presence of
oxygen.
2N2O (g)
+
3O2 (g) 
4NO2 (g)
a. 9.00 grams of laughing gas react. How many moles of oxygen react?
b. If 7.50 grams of oxygen react, how many grams of smog are produced?
3. The acid in your stomach that aids in breaking down proteins is called hydrochloric acid, HCl.
Occasionally the glands that produce the HCl make more than is needed and you get those nasty sour
burps. You can neutralize the excess acid by taking milk of magnesia. The active ingredient in milk of
magnesia is Mg(OH)2. The chemical reaction is shown below.
2 HCl + Mg(OH)2

MgCl2 +
2H2O
a. If you drink 2.00 grams of Mg(OH)2, how many moles of HCl are neutralized?
4. Consider the double replacement reaction below. The lead(II) idodide is a bright yellow insoluble
substance. Prior to the 1960’s it was used as a dye in yellow paint. Lead poisoning could result if you eat
the paint so is different dye is used in today’s paint.
Sodium iodide + lead (II) nitrate  Sodium nitrate + Lead (II) iodide
a. Write a balanced reaction.
b. If 10.0 grams of sodium iodide react, how many grams of lead (II) iodide are produced.
5. Use the balanced chemical reaction for the combustion of propane, C 3H8, to answer the questions
below.
C3H8 + 5 O2  3 CO2 + 4 H2O
a) A student conducts an experiment using the reaction above. When she burns 44.0 grams of propane, 160.0
grams of oxygen is consumed. 132 grams of carbon dioxide and 72 grams of water are produced. Does this data
support the Conservation of Mass? How are these masses related to the coefficients in the balanced reaction?
Use the masses given to support both of your answers.
When two or more substances combine to form a single product, the reaction is called a synthesis reaction.
For example, the formation of water from hydrogen and oxygen gases is a synthesis reaction:
2H2 (g) + O2 (g)  2H2O (l)
synthesis
In a decomposition reaction, a compound breaks down into two or more simpler substances. For example,
in electrolysis, water is broken down into hydrogen and oxygen gases:
2H2O (l)  2H2 (g) + O2 (g)
decomposition
Decomposition and synthesis are opposite chemical processes.
Problem Set 5.5
Classify each of the following as a single replacement , double replacement reaction, synthesis, or
decomposition
a.
c.
e.
MX + Z  MZ + X
M + X  MX
2KI + CaO  K2O + CaI2
b.MX  M + X
d. MX + YZ  MZ + YX
f. NaCl  Na + Cl2
_
g. BaS + MgO  BaO + MgS
h. 2H2 + O2  2H2O
i. H2SO4 + FeS  H2S + FeSO4
j. 2NH4Cl + F2  Cl2 + 2NH4F
The concentration of a solution is the amount of solute contained in a certain volume of solution. If a solution
contains a small amount of solute it is called dilute, and if it contains a large amount of solute it is called
concentrated.
In chemistry, concentration is given as molarity, (M), the number of moles (mol) of the solute in one liter
(L) of solution and expressed as moles/liter or just M.
Topic 6:
Solutions
Topic 7:
Experimentation
Problem Set 6.5
Show work or you will not receive credit.
1.What is the molarity of a 2.0L solution that was made up with 4.0 moles of NaCl?
2. How many liters of solution are needed to make a 0.5M solution with 2.0 moles of BaCl 2?
3. How many moles of Na2CO3 are there in 10.0 L of 2.0M solution?
4. How many moles of Na2CO3 are in 10.0 L of a 4.0M solution?
5. 4 moles of HNO3 (Nitric Acid) are dissolved in water to 5L. What is the molarity of the solution?
6. 71.5g of AgCl (MW=143amu) are dissolved in 2L of NH3 (ammonia). What is the
molarity of the solution?
7. Seawater contains roughly 28.0 g of NaCl per liter. What is the molarity of sodium chloride in seawater?
8. How many grams of KNO3 are needed to make 2 Liters of a 0.5 M solution?
9. How many moles of NaCl are contained in 100.0 mL of a 0.20M solution?
10. What mass (in grams) of NaCl would be contained in 500mL of 0.5M solution?
11. A scientist needs 500 ml of 1.0 M HCl (hydrochloric acid). The stock solution on the shelf is 12 M HCl,
how much of this stock solution will he need to dilute to 500 ml in order to get the 1.0 M solution he needs for
his experiment:
12. Joe Chemistry Student has 100 ml of 6.0 M HCl solution. Will this be enough to make a liter of 2.0 M
HCL?
13. A 25.0 mL sample of concentrated H3PO4 (14.7 M) is diluted to a final volume of 500.0 mL. What is the
molarity of the final solution?
14. Fluoxymesterone, C20H29FO3, is an anabolic steroid. A solution is prepared by dissolving 10.0 g of the
steroid in 500.0 mL of water Then 5 ml of this solution is diluted to a 100mL total volume? What is the final
M of the diluted solution.
15. What volume (mL) of concentrated HF (16.5 M) should be used to prepare 125.0 mL of a 0.350 M solution?
16. What volume (mL) of concentrated HCl (12.1 M) should be used to prepare 250.0 mL of a 0.500 M
solution?
17. Which of the following would raise the boiling point the highest?
a. 0.001 M
b. 0.01 M c. 0.1 M d. 1 M
18. Which of the following would lower the freezing point the lowest?
a. 0.001 M
b. 0.01 M c. 0.1 M d. 1 M
Given a graph of experimental data, identify the independent variable (x-axis) and the dependent variable
(y-axis) and interpret the relationship between the variables.
A pipette is used to add the final amount of solvent to a volumetric flask to ensure a precise concentration of a
solution.
Extra Material For Unit 5
1.
2.
3.
4.
5.
6.
7.
Solutions can be a variety of solute/solvent combinations, such as gas/gas, gas/liquid, liquid/liquid, solid/liquid,
gas/solid, liquid/solid, or solid/solid. An example of gas/gas would be air, where the solutes are O 2, CO2, and
small amounts of He and other gases, the solvent is N2 because it is present in the largest amount. Bronze is an
example of a solid/solid solution because it is a homogeneous mixture of copper and tin. Be able to give examples
and recognize solutions of all the different combinations.
A solution with a known molarity can be mixed with different amounts of water to make solutions of varying
dilutions. Each dilute solution’s molarity can be calculated using the following equation, M1 x V1 = M2 x V2,
where M1 and V1 are the initial solution’s molarity and volume. M2 and V2 are the final solution’s molarity and
volume. Use this equation to solve for the unknown variable, when three of the variables are known.
A property that depends on the concentration (number) of solute particles but is independent of their nature is
called a colligative property. Four colligative properties, vapor pressure reduction, boiling point elevation,
freezing point depression, and osmotic pressure are explained below.
Vapor pressure is the pressure produced when vapor particles above a liquid in a sealed container collide with the
container walls. Equilibrium exists between the vapor and the liquid when the number of molecules in the vapor
state remains constant. This pressure is reduced when a solute is dissolved in the solvent. Vapor pressure
reduction is directly related to the concentration of solute particles.
The boiling point, the temperature at which the vapor pressure of a liquid equals atmospheric pressure, of a
solvent is raised when a solute is dissolved in the solvent. This boiling point elevation is directly related to the
concentration of a solution.
Freezing point is the temperature at which the solid and liquid form of a substance exists in equilibrium. As
solute particles are added to a solvent the freezing point is lowered. The freezing point depression is directly
related to the concentration of a solution.
Osmosis is the diffusion of water across a selectively permeable membrane. Osmotic pressure is the measure of
the tendency of a solution to take up water when separated from pure water by a selectively permeable membrane.
Increasing the solute concentration in a solution increases the osmotic pressure.
Unit 5 Practice Quiz
1.
2.
CaCO3 + Al(NO3)3  Ca(NO3)2 + Al2(CO3)3
When the above equation is balanced the coeffiecients in order are
a. 3,2,1,1 b. 3,2,3,1 c. 3,1,3,2 d. 3,2,2,1
Use the balanced equation for the formation of rust to answer questions #2-5
4Fe + 3O2  2Fe2O3
What is the mole ratio between oxygen and rust?
a. 3:2
b. 2:3
c. 4:3
d. 4:2
3.
How many moles of rust (Fe2O3) forms from 560 grams of iron?
a. 2.5 moles
b. 1.25 moles
c. 5 moles
d. 56 moles
4.
How many grams of iron will completely react with 8.00 grams of O 2?
a. 60 g b. 14 g
c. 18.7 g
d. 8.00 g
5.
How many grams of oxygen are needed to needed to form 1 mole of rust?
a. 3 grams b. 32 grams c. 48 grams
d. 96 grams
6.
What is the charge on iron in rust Fe 2O3?
b. 2+
b. 3+
c. 6+
7.
d. 2-
Which is lead (II) hydroxide?
a. PbOH b. Pb2OH c. Pb(OH)2 d. Pb(II)OH
8.
What type of compound is ammonium hydroxide, NH 4OH?
c. Metallic b. Ionic c. covalent
d. nuclear
d.
Use the energy diagram to answer questions #9-#11
9.
Which number represents the effect of a catalyst on the activation energy?
a. 1
b. 2
c. 3
d. 4
10.
11.
What type of reaction does this diagram represent?
a. Endothermic
b.Exothermic
c. synthesis
What does #1 represent?
a. delta H b. PE products
c. PE reactants
d. decomposition
d. Ea of the reverse reaction
12.
What is the molarity of a solution containing 2 moles of NaCl in 500 ml of solution?
a. 4 M
b. 2M
c. 8 M
d. 1000 M
13.
What is the name of Fe3N2?
e. Iron(III) nitride b. Iron(II) nitride c. Triiron dinitride d. Iron Nitrate
14.
How many grams of NaCl would be needed to make 4 L of a 0.5 M solution?
a. 0.5grams
b. 116 grams
c. 29 grams
d. 58 gram
15.
What is the trend in atomic radii on the periodic table?
f. Increase left to right, Increase top to bottom
g. Decrease left to right, Increase top to bottom
h. Increase left to right, decrease top to bottom
i. Decrease left to right, decrease top to bottom