Ch. 11 and Ch. 12 discuss Chemical Reactions and Stoichiometry. It talks about writing, balancing, classifying, and predicting products of chemical reactions. Ch. 12 talks about arithmetic of equations, interpreting chemical equations, mole ratios, reagants, and yields.
Group 1 (Co-Editor Elizabeth Howard)
Olivia Richardson pg 321-323
Writing Chemical Equations
Chemical reactions are happening all around us, all the time.
In a chemical reactions on or more substances (the reactants) change into one or more new substances (the products)
For example when baking bread the ingredients, flour, salt, yeast, and water would be the reactants and the bread
would be the product.
To write out these reactions chemists us a quick shorthand notation called a chemical equation.
Word Equations
To write a word equation, write the names of the reactants to the left of the arrow separatd by plus signs; write th names of the products to the right of the arrow, also separated by plus signs.
The word equation describing the rusting of iron is: iron + oxide -----> iron(III) oxide
Thee word equation for "Hydrogen peroxide decomposes to form water and oxygen gas" would be:
hydrogen peroxide -----> water + oxygen Chemical Equations
A chemical equation is a representation of a chemical reaction;the formulas of the reactants (on the left) ar connectd by an arrow with the formulas of the products (on th right)
A skeleton equation is a chemical equation that does not indicate the relative amounts of the reactants and products
Write the formulas of the reactants to the left of the yields sign (arrow) and the formulas of the products to the right.
You can state the physical state of substances by using symbols like (s) for solid, (l) for liquid, (g) for a gas, and (aq) for substance in aqueous.
For example the equation for rusting with symbols for the physical states added is: Fe(s) + O2(g)---->Fe2O3(s)
A catalyst is a substance that speeds up the reaction but is not usd up in the reaction and is added to the reaction mixture.
It is neither a reactant nor a product
Elizabeth Howard pg 324-326
Balancing Chemical Equations
An unbalanced equation does not indicate the quantity of reactants needed to make the product.
A balanced equation must indicate the kinds of parts required and also the quantities of the parts required.
A chemical equation has two parts: the reactants and products
A bicycle can be used to demonstrate a balanced chemical equation
The reactants are the Frame (F), Wheel (W), Handlebar (H), Pedal (P) and the product is the bicycle
F + W + H + P à Bicycle
This formula shows the parts necessary to make the bicycle, but not the quantities of each part
The correct equation for a bicycle would be F + 2W + H + 2P à FW2HP2
· This method can be used to balance chemical equations · A Balanced Equation is a chemical equation in which mass is conserved; each side of the equation has the same number of atoms of each element. · Balanced Equations include coefficients, which are small whole numbers that appears in front of a formula in a balanced chemical equation. Coefficients that are equal to 1 are not written · Balanced Equations follow Dalton’s Theory that says atoms are not created nor destroyed; they are only rearranged. · To write a balanced chemical equation, first write the skeleton equation. Then use coefficients to balance the equation so that it obeys the law of conservation of mass. · In all balanced equations, each side of the equation have the same number of atoms of each element. · This is the equation for the burning of hydrogen: o H2 + O2 à H2O o This equation is not balanced because the reactants contain two hydrogen and two oxygen, but the product contains two hydrogen but only one oxygen o The correct balanced equation is 2H2 + O2 à 2H2O
Nathan Lynch pg 327-329
Nate Lynch (327-329)
Rules for Balancing
1) The same # and type of atom must be present on each side of the equation.
2) Balancing is accomplished by adding coefficients. NEVER change the subscripts.
3) Coefficients must be in the smallest whole # ratio.
4) Balancing is done by trial and error.
5) Balance H’s and O’s last.
6) Balance polyatomic ions as one unit.
example: 2H2 + O2 --> 2H2
Skeleton equations are also known as unbalanced equations.
Group 2 (Co-Editor Becky Hyatt)
Becky Hyatt pg 330-332
Classifying Reactions (pg 330)
the five general types of reaction are combination, decomposition, single-replacement, double-replacement, and combustion
Combination Reactions (pg 330)
a combination reaction is a chemical change in which two or more substances react to form a single new substance
2Mg(s) + O2(g) = 2MgO(s)
the reactants are Mg and O2 and the product is MgO
Conceptual Problem 11.4 (pg 331)
Writing Equations for Combination Reactions:
Copper and sulfur are the reactants in a combination reaction. Complete the equation for the reaction.
Cu(s) + S(s) = (two reactions possible)
Analyze- identify the relevant concepts
determine the formulas for the 2 products and balance the 2 possible equations
Solve- apply concepts to this situation
write the skeleton equation first, then apply the rules for balancing equations
Practice Problem:
Complete and balance this equation fir a combination reaction. Be + O2 =
Decomposition Reactions (pg 332)
a decomposition reaction is a chemical change in which a single compound breaks down into two or more simpler products
2HgO(s) = 2Hg(l) + O2(g)
Conceptual Problem 11.5 (pg 332)
Writing the Equation for a Decomposition Reaction:
Decomposition reactions that produce gases and heat are sometimes explosive. Write a balanced equation for the following decomposition reaction.
H2O(l) =(electricity)
Analyze- identify the relevant concepts
balance the equation, remembering that hydrogen and oxygen are both diatomic molecules
Solve- apply concepts to this situation
write the skeleton equation, then apply the rules for balancing equations
Practice Problem:
Complete and balance this decomposition reaction. HI = http://www.youtube.com/watch?v=0vgOcR5XQlM - a link for more help with types of chemical reactions
Single-Replacement Reactions
Andrea Luongo pg 333-335
Single-Replacement Reaction is a chemical change in which one element replaces a second element in a compound.
Both the reactants and products contain an element and compound in a single-replacement reaction.
When a piece of Potassium mixes with water, it produces hydrogen gas and a large quantity of heat.
2K(s) + 2H20(l) ---> 2KOH(aq) + H2(q)
When a piece of Zinc placed into Copper nitrate, the reaction is:
Zn(s) + Cu(NO3)2 (aq) ---> Cu(s) + Zn(NO3)2 (aq)
In this reaction, Zinc and Copper change places.
Single-Replacement Reaction:
Activity Series of Metals is a list of metals in order of decreasing reactivity.
Metals displace with other metals depending on the relative reactivities of the two metals.
Active metals in the series can replace any metal below it in that series.
A halogen can replace another halogen from a compound.
Activity of halogens decreases going down Group 7A of the periodic table.
When a less active element is the reactant, then there is no reaction.
Activity Series of Metals:
Double-Replacement Reactions
By Andrea Luongo page 333-335
Double-Replacement Reaction is a chemical change involving an exchange of positive ions between two compounds.
Double-replacement reaction are also known as double-displacement reactions.
This usually takes place between an aqueous solution and a precipitate, gas, or molecular compound.
True of Double-Replacement Reactions:
One of the products is soluble and the precipatates form a solution.
One product is a gas.
One product is a molecular compound.
Double-Replacement Reactions:
For more help with Double-Replacement Reactions visit:
a combustion raction is a chemical change in which an element or a compoujd reacts with an element or a compound reacts with oxygen often producing energy in the form of heat or light.
the combustion produces carbon dioxide or else the reaction is not complete
Predicting the Prouducts of a Chemical Equation Page 337
In a combustion reaction two or more elements and compounds combine to form a single product
In a decomposition reaction a single compound is the reactant and two or more substances are the product
Group 3 (Co-Editor Alex Nunan)
Christian Cooke pg 342
Many important chemical reactions take place in water-that is, an aqueous solution. The reactants and one of the products separate into cations and anions when they dissolve in water complete ionic equation- equation that shows dissolved ionic compounds as dissociated free ions
· Mixing two ionic compounds can sometimes form precipitates · Not all solutions form participates · Key Note – You can predict the formation of a precipitate by using the rules of solubility of ionic compounds.
Solubility Rules for Ionic Compounds
Compounds
Solubility
Salts and alkali metals and ammonia
Soluble
Nitrate salts and chlorate salts
Soluble
Sulfate salta except compounds with Pb2+, Ag+, Hg22+, Ba2+, Sr2+, and Ca2+
Soluble
Chloride salts except compound with Ag+, Pb2+, and Hg22+
Soluble
Carbonates, phosphates, chromates, sulfides, and hydroxides
Most are insoluble
**When compounds are insoluble, they can form precipitates.
Here is a work sheet and answer key to help give you some examples on how to tell which product of a reaction will be a percipitate.
-Nearly Everything you use is manufactured form chemicals - soaps, shapoos, CDs, cosmetics, medicines and cloths
The chemical process used in manufacturing must be carried out economically, which is where balenced equations help
A balenced chemical equation tells you what amounts of reactants to mix and what amounts of product to expect. (how much to put into the mixture and how much will be produced.)
This is an example of a balenced equataion
Chemists use balanced chemical equations as a basis to caculate how much reactant is needed or product is formed in a reaction.
When you know the quantity of one substance in a reaction, you can caculate the quantity of any other substance consumed or created in a reaction.
*Quantity - the amounts of a substance expressed in grams or moles* could also be in liters, rons or molecules
Stoichiometry
-Stoichiometry- the calculation of quantities in chemical reactions is a subject of chemistry called stoichiometry
Caculations using balanced equations are called Stoichiometric calculations
Chemists can track reactants and products in a reaction by stoichiometry.
It allows chemists to tally the amounts of reactants and products using ratios of moles or pepresentative particles
Below is a video explaining how to do stoichiometry....it is basically a more complex version of what we have been doing in class and is a good video to watch.
The balanced chemical equation tells you the relative amounts of reactants and products in the reaction
Key concept: A balanced chemical equation can be interpreted in terms of different quantities, including number of atoms, molecules, or moles; mass; and volume
Your interpretation of the equation depends on how you quantify the reactants and the products
In the following explanations of interpreting chemical equations, ammonia will be used as an example to make it easier to understand
Ammonia is most commonly used as a fertilizer
Ammonia is produced industrially by the reaction of nitrogen with hydrogen, below is the chemical equation for this reaction
. N2 + 3H2 à 2NH3
Number of Atoms
For the atomic level, a balanced equation indicates that the number and type of each atom that makes up each reactant also makes up each product
Both the number and the types of atoms are not changed in reactions
In the synthesis of ammonia, the reactants consist of 2 nitrogen atoms and 6 hydrogen atoms, these 8 atoms are recombined in the product
Number of Molecules
For molecules, the balanced equation indicates that one molecule of nitrogen reacts with the three molecules of of hydrogen
Nitrogen and hydrogen will always react to form ammonia in a 1:3:2 ratio
You can also take Avogadro's number of nitrogen molecules and make them react with three times Avogadro's number of hydrogen molecules
Moles
A balanced equation also tells you the number of moles of reactants and products
The coefficients of a balanced equation indicate the relative numbers of the moles of the reactants and products in a chemical reaction, this is the most important information that a balanced chemical equation can provide for you, using this information, you can calculate the amounts of reactants and products
In the synthesis of ammonia, one mole of nitrogen molecules reacts with three moles of hydrogen molecules to form two moles of ammonia molecules, as you can tell, the number of moles in the reactant doesn't equal the total number of moles in the product
Mass
Balanced chemical equations have to follow the laws of conservation of matter
The number and types of atoms doesn't change in a chemical reaction, therefore, the total mass of the atoms in the reaction doesn't change either
The mass of 1 mol of N2 (28 grams) plus the mass of 3 mol of H2 (6 grams) equals the mass of 2 mol of NH3 (34 grams)
Volume
1 mol of any gas at STP occupies a volume of 22.4 L.
The equation shows that 22.4 L of N2 reacts with 67.2 L (3 x 22.4 l) of H2. This reaction forms 44.8 L (2 x 22.4 L) of NH3
Mass Conservation in Chemical Reactions
The mass of the reactants equals the mass of the products
The number of the the atoms of each type in the reactants equals the number of atoms of each type in the product
Key concept: Mass and atoms are conserved in every chemical reaction
Molecules, formula units, moles, and volumes may not necessarily be conserved, however they could be.
As an example, use hydrogen iodide: H2 + I2 à 2HI
In this reaction, molecules, moles, and volume are all conserved, but in most chemical reactions, they arent
Here is a good link for more information on Interpreting Chemical equations, and other topics involving stoichiometry:
Mole ratio- a conversion factor that derived from the coefficients of a balanced Chemical equation interpreted in terms of moles. http://www.youtube.com/watch?v=zw0CT63AK1I - a link that may help with the mole calculations.
Brandon Boisclair page 365-367
SAMPLE PROBLEM:
Nitrogen monoxide and oxygen gas combine to form the brown gas nitrogen dioxide, which contributes to photochemical smog. How many liters of nitrogen dioxide are produced when 34 L of oxygen reacts with an excess of nitrogen monoxide?
2NO(g) + O2(g) -----> 2NO2(g)
DON'T FORGET:
1. Analyze -List the known and the unknown
KNOWN:
-Volume of Oxygen = 34 L O2
-2 mol NO2/ 1 mol O2 (Mole ratio from balanced equation)
-1 mol O2 = 22.4 L O2
-1 mol NO2 = 22.4 L O2
2. Calculate- Solve for the unknown
34 L O2 X 1 mol O2 X 2 mol NO2 X 22.4 L NO2 = 68 L NO2
22.4 L O2 1 mol O2 1 mol NO2
3. Evaluate- Does the result make sense
Because 2 mol NO2 is produced for each 1 mol O2 that reacts, the volume of NO2 should be twice the given volume of O2. The answer should have two significant figures.
Zoey Killion page 362-364
Sample Problems 12.3 (page 362)
Zoey Killion
Finding the Mass of a Product:
Analyze: List the known and the unkown
Calculate: Solve for the unknown.
Evaluate: Does the result make sense?
Example:
Calculate the number of grams of NH3 produced by the reaction of 5.40g of hydrogen with an excess of nitrogen. The balanced equation is: N2(g) + 3H2(g) --> 2NH3(g). Step 1: (Analyze) Knowns:
Mass of hydrogen = 5.40g H2
1 mol H2 = 2.0 g H2 (molar mass)
1 mol NH3 = 17.0 g NH3 (molar mass)
Unkown:
mass of ammonia = ? g NH3
Step 2: (Calculate)
This following series of caluculations can be combined:
g H2 --> mol H2 --> mol NH3 --> g NH3
5.04 g H2 X (1 mol H2/ 2.0 g H2) X (2 mol NH3/ 3 mol H2) X (17.0 g NH3/ 1 mol NH3) = 31 g NH3 Step 3: (Evaluate)
Because the molar mass of NH3 is substantially greather than the molar mass of H2, the answer should have a larger mass than the given mass. The answer should have two (2) significant figures. More Practice Problems:
Acetylene gas (C2H2) is produced by adding water to calcium carbide (CaC2). CaC2(s) + 2H20(l) ---> C2H2(g) + Ca(OH)2(aq). How many grams of acetylene are produced by adding water to 5.00 g CaC2?
Using the same equation, determine how many moles of CaC2 are needed to react completely with 49.0 g H20.
Other Stoichiometric Calculations: (page 363)
Zoey Killion
In any of these problems, the given quantity is first converted to moles. Then the mole ratio from the balanced equation is used to calculate the number of moles of the wanted substance. Finally, the moles are converted to any other unit of measurement related to the unit mole.
aG (given quantity) -----> bW (wanted quantity)
Sample Problems 12.4: (page 364)
Zoey Killion
Calculating the Molecules of a Product:
Analyze: List the known and the unkown
Calculate: Solve for the unknown.
Evaluate: Does the result make sense?
Example:
Figure 1: The electrolysis of water causes it to decompose into hydrogen and oxygen.
How many molecules of oxygen are produced when a sample of 29.2 g of water is decomposedby electrolysis, as shown in Figure 1? The balanced equation is:
2H20(l) ------> (electricity) 2H2 (g) + O2 (g) Step 1: (Analyze) Knowns:
mass of water = 29.2 g H20
1 mol H20 = 18.0 g H20 (molar mass)
1 mol O2 = 6.02 X 10^23 molecules of O2
Unknown:
molescules of oxygen = ? molecules of O2
Step 2: (Calculate)
2.92 g H2O X (1 mol H20/ 18.0 g H2O) X (1 mol O2/ 2 mol H2O) X (6.02 X 10^23 molecules of O2/ I mol O2) = 4.88 X 10^23 molecules O2 Step 3:
The given mass of water should produce a little less than 1 mol of oxygen, or a little less then Avogadro's number of molecules. The answer should have three (3) significant figures. More Practice Problems:
How many molecules of oxygen are produced by the decomposition of 6.54 g of potassium chlorate (KClO3)? 2KlO3(s) ---> 2KCl(s) + 3O2(g).
The last step in the production of nitric acid is the reaction of nitrogen dioxide with water. 3NO2(g) + H2O(l) ----> 2HNO3(aq) + NO(g). How many grams of nitrogen dioxide must react with water to produce 5.00 X 10^22 molecules of nitrogen monoxide?
The coefficients in a chemical equation indicate the relative number of particles and the relative number of moles of reactants and products. For a reaction involving gaseous reactants or products, the coefficients also indicate relative amounts of each gas. As a result, you can use volume ratios in the same way you ahve used mole ratios. For more help with Stoichiometric Calculations watch this video: http://www.youtube.com/watch?v=TGJARI7cXrU
Group 6 (Co-Editor Haley Conatser)
Mitch Martin and Dakota pg 368-371
. In a Chemical reaction, an insufficient quantity of any of the reactants will limit the amount of product that forms.
Limiting reagent: reagent that determines the amount of product that can be formed in a reaction.
Excess reagent: Not completely used up in the reaction.
Editor:James Payne
Ch. 11 and Ch. 12 discuss Chemical Reactions and Stoichiometry. It talks about writing, balancing, classifying, and predicting products of chemical reactions. Ch. 12 talks about arithmetic of equations, interpreting chemical equations, mole ratios, reagants, and yields.
Group 1 (Co-Editor Elizabeth Howard)
Olivia Richardson pg 321-323
Writing Chemical Equations
- Chemical reactions are happening all around us, all the time.
- In a chemical reactions on or more substances (the reactants) change into one or more new substances (the products)
For example when baking bread the ingredients, flour, salt, yeast, and water would be the reactants and the breadwould be the product.
- To write out these reactions chemists us a quick shorthand notation called a chemical equation.
Word Equations- To write a word equation, write the names of the reactants to the left of the arrow separatd by plus signs; write th names of the products to the right of the arrow, also separated by plus signs.
- The word equation describing the rusting of iron is: iron + oxide -----> iron(III) oxide
- Thee word equation for "Hydrogen peroxide decomposes to form water and oxygen gas" would be:
hydrogen peroxide -----> water + oxygenChemical Equations
- A chemical equation is a representation of a chemical reaction;the formulas of the reactants (on the left) ar connectd by an arrow with the formulas of the products (on th right)
- A skeleton equation is a chemical equation that does not indicate the relative amounts of the reactants and products
- Write the formulas of the reactants to the left of the yields sign (arrow) and the formulas of the products to the right.
- You can state the physical state of substances by using symbols like (s) for solid, (l) for liquid, (g) for a gas, and (aq) for substance in aqueous.
For example the equation for rusting with symbols for the physical states added is: Fe(s) + O2(g)---->Fe2O3(s)- A catalyst is a substance that speeds up the reaction but is not usd up in the reaction and is added to the reaction mixture.
- It is neither a reactant nor a product
Elizabeth Howard pg 324-326Balancing Chemical Equations
- An unbalanced equation does not indicate the quantity of reactants needed to make the product.
- A balanced equation must indicate the kinds of parts required and also the quantities of the parts required.
- A chemical equation has two parts: the reactants and products
- A bicycle can be used to demonstrate a balanced chemical equation
- The reactants are the Frame (F), Wheel (W), Handlebar (H), Pedal (P) and the product is the bicycle
- F + W + H + P à Bicycle
- This formula shows the parts necessary to make the bicycle, but not the quantities of each part
- The correct equation for a bicycle would be F + 2W + H + 2P à FW2HP2
· This method can be used to balance chemical equations· A Balanced Equation is a chemical equation in which mass is conserved; each side of the equation has the same number of atoms of each element.
· Balanced Equations include coefficients, which are small whole numbers that appears in front of a formula in a balanced chemical equation. Coefficients that are equal to 1 are not written
· Balanced Equations follow Dalton’s Theory that says atoms are not created nor destroyed; they are only rearranged.
· To write a balanced chemical equation, first write the skeleton equation. Then use coefficients to balance the equation so that it obeys the law of conservation of mass.
· In all balanced equations, each side of the equation have the same number of atoms of each element.
· This is the equation for the burning of hydrogen:
o H2 + O2 à H2O
o This equation is not balanced because the reactants contain two hydrogen and two oxygen, but the product contains two hydrogen but only one oxygen
o The correct balanced equation is 2H2 + O2 à 2H2O
Nathan Lynch pg 327-329
Nate Lynch (327-329)
Rules for Balancing
1) The same # and type of atom must be present on each side of the equation.
2) Balancing is accomplished by adding coefficients. NEVER change the subscripts.
3) Coefficients must be in the smallest whole # ratio.
4) Balancing is done by trial and error.
5) Balance H’s and O’s last.
6) Balance polyatomic ions as one unit.
example: 2H2 + O2 --> 2H2
Skeleton equations are also known as unbalanced equations.
Group 2 (Co-Editor Becky Hyatt)
Becky Hyatt pg 330-332
Classifying Reactions (pg 330)
Combination Reactions (pg 330)
Conceptual Problem 11.4 (pg 331)
Writing Equations for Combination Reactions:Copper and sulfur are the reactants in a combination reaction. Complete the equation for the reaction.
Cu(s) + S(s) = (two reactions possible)
- Analyze- identify the relevant concepts
- determine the formulas for the 2 products and balance the 2 possible equations
- Solve- apply concepts to this situation
- write the skeleton equation first, then apply the rules for balancing equations
Practice Problem:Complete and balance this equation fir a combination reaction. Be + O2 =
Decomposition Reactions (pg 332)
Conceptual Problem 11.5 (pg 332)
Writing the Equation for a Decomposition Reaction:Decomposition reactions that produce gases and heat are sometimes explosive. Write a balanced equation for the following decomposition reaction.
H2O(l) =(electricity)
- Analyze- identify the relevant concepts
- balance the equation, remembering that hydrogen and oxygen are both diatomic molecules
- Solve- apply concepts to this situation
- write the skeleton equation, then apply the rules for balancing equations
Practice Problem:Complete and balance this decomposition reaction. HI =
http://www.youtube.com/watch?v=0vgOcR5XQlM - a link for more help with types of chemical reactions
Single-Replacement Reactions
Andrea Luongo pg 333-335
- Single-Replacement Reaction is a chemical change in which one element replaces a second element in a compound.
- Both the reactants and products contain an element and compound in a single-replacement reaction.
- When a piece of Potassium mixes with water, it produces hydrogen gas and a large quantity of heat.
- 2K(s) + 2H20(l) ---> 2KOH(aq) + H2(q)
- When a piece of Zinc placed into Copper nitrate, the reaction is:
- Zn(s) + Cu(NO3)2 (aq) ---> Cu(s) + Zn(NO3)2 (aq)
- In this reaction, Zinc and Copper change places.
Single-Replacement Reaction:Activity Series of Metals:
Double-Replacement Reactions
By Andrea Luongo page 333-335
One of the products is soluble and the precipatates form a solution.
One product is a gas.
One product is a molecular compound.
Double-Replacement Reactions:
For more help with Double-Replacement Reactions visit:
http://www.youtube.com/watch?v=ul4xRy8hcsQDouble-Replacement Reaction
Big Dan's Restaraunt pg 336-339
Combustion Reactions Page 336
Writing Equations for Combustion Reactionsa combustion raction is a chemical change in which an element or a compoujd reacts with an element or a compound reacts with oxygen often producing energy in the form of heat or light.
the combustion produces carbon dioxide or else the reaction is not complete
Example 1) C6H6(l) + O2(g) -----> CO2(g) +H2O(g)
BALANCED EQUATION) 2C6H6(l) + 15O2(g) ------> 12CO2(g) + 6H20(l)
Predicting the Prouducts of a Chemical Equation Page 337
Group 3 (Co-Editor Alex Nunan)
Christian Cooke pg 342
Many important chemical reactions take place in water-that is, an aqueous solution.The reactants and one of the products separate into cations and anions when they dissolve in water
complete ionic equation- equation that shows dissolved ionic compounds as dissociated free ions
EX: Ag+ (aq) + NO3 - (aq) + Na+(aq) + Cl-(aq) -------> AgCl (s) + Na+(aq) + NO3-(aq)
Alex Nunan pg 343
key terms:
spectator ion- an ion appears on both sides of an equation and is not directly involved in the reaction:net ionic equation- an equation for a reaction in a solution that shows only those particles that are directly involved in the chemical change:
sample:
Ag+(aq) + Cl-(aq) --> AgCl(s)Pb(s) + AgNO3(aq) --> Ag(s) + Pb(NO3)2(aq)
- this is the skeleton equation for the reaction of lead with silver nitrate
Pb(s) + Ag+(aq) --> Ag(s) + Pb2+(aq)- this is the net ionic equation, unbalanced
Pb(s) + 2Ag+(aq) --> 2Ag(s) + Pb2+(aq)A net ionic equation shows only those particles involved in the reaction and is balanced with respect to both mass and charge.
Watch this video for more help!
http://www.youtube.com/watch?v=I2liasSXCXM
Shannon Lamy pg 344
Predicting the Formation of Precipitates
· Mixing two ionic compounds can sometimes form precipitates
· Not all solutions form participates
· Key Note – You can predict the formation of a precipitate by using the rules of solubility of ionic compounds.
Solubility Rules for Ionic Compounds
**When compounds are insoluble, they can form precipitates.
Here is a work sheet and answer key to help give you some examples on how to tell which product of a reaction will be a percipitate.
Group 4 (Co-Editor Peter Hamill)
PJ Hamill page 353
Caroline Rubino page 354-355
Using Balenced Chemical Equations
-Nearly Everything you use is manufactured form chemicals - soaps, shapoos, CDs, cosmetics, medicines and cloths
The chemical process used in manufacturing must be carried out economically, which is where balenced equations help
A balenced chemical equation tells you what amounts of reactants to mix and what amounts of product to expect. (how much to put into the mixture and how much will be produced.)
Chemists use balanced chemical equations as a basis to caculate how much reactant is needed or product is formed in a reaction.
When you know the quantity of one substance in a reaction, you can caculate the quantity of any other substance consumed or created in a reaction.
*Quantity - the amounts of a substance expressed in grams or moles* could also be in liters, rons or molecules
Stoichiometry
-Stoichiometry- the calculation of quantities in chemical reactions is a subject of chemistry called stoichiometry
Caculations using balanced equations are called Stoichiometric calculations
Chemists can track reactants and products in a reaction by stoichiometry.
It allows chemists to tally the amounts of reactants and products using ratios of moles or pepresentative particles
Mike Hanley page 356-358
Interpreting Chemical Equations
- Ammonia is produced industrially by the reaction of nitrogen with hydrogen, below is the chemical equation for this reaction
. N2 + 3H2 à 2NH3Number of Atoms
Number of Molecules
Moles
Mass
Balanced chemical equations have to follow the laws of conservation of matter
Volume
- 1 mol of any gas at STP occupies a volume of 22.4 L.
- The equation shows that 22.4 L of N2 reacts with 67.2 L (3 x 22.4 l) of H2. This reaction forms 44.8 L (2 x 22.4 L) of NH3
Mass Conservation in Chemical ReactionsChart for Interpreting Chemical Equations
Group 5 (Co-Editor Brandon Boisclair)
Evan Sommerich pg 359-361
Writing and Using mole Ratios
Mole ratio- a conversion factor that derived from the coefficients of a balanced Chemical equation interpreted in terms of moles.http://www.youtube.com/watch?v=zw0CT63AK1I - a link that may help with the mole calculations.
Brandon Boisclair page 365-367
SAMPLE PROBLEM:Nitrogen monoxide and oxygen gas combine to form the brown gas nitrogen dioxide, which contributes to photochemical smog. How many liters of nitrogen dioxide are produced when 34 L of oxygen reacts with an excess of nitrogen monoxide?
2NO(g) + O2(g) -----> 2NO2(g)
DON'T FORGET:
1. Analyze -List the known and the unknown
KNOWN:
-Volume of Oxygen = 34 L O2
-2 mol NO2/ 1 mol O2 (Mole ratio from balanced equation)
-1 mol O2 = 22.4 L O2
-1 mol NO2 = 22.4 L O2
2. Calculate- Solve for the unknown
34 L O2 X 1 mol O2 X 2 mol NO2 X 22.4 L NO2 = 68 L NO2
22.4 L O2 1 mol O2 1 mol NO2
3. Evaluate- Does the result make sense
Because 2 mol NO2 is produced for each 1 mol O2 that reacts, the volume of NO2 should be twice the given volume of O2. The answer should have two significant figures.
Zoey Killion page 362-364
Sample Problems 12.3 (page 362)Zoey Killion
Finding the Mass of a Product:
- Analyze: List the known and the unkown
- Calculate: Solve for the unknown.
- Evaluate: Does the result make sense?
Example:Calculate the number of grams of NH3 produced by the reaction of 5.40g of hydrogen with an excess of nitrogen. The balanced equation is: N2(g) + 3H2(g) --> 2NH3(g).
Step 1: (Analyze)
Knowns:
- Mass of hydrogen = 5.40g H2
- 1 mol H2 = 2.0 g H2 (molar mass)
- 1 mol NH3 = 17.0 g NH3 (molar mass)
Unkown:- mass of ammonia = ? g NH3
Step 2: (Calculate)This following series of caluculations can be combined:
g H2 --> mol H2 --> mol NH3 --> g NH3
5.04 g H2 X (1 mol H2/ 2.0 g H2) X (2 mol NH3/ 3 mol H2) X (17.0 g NH3/ 1 mol NH3) = 31 g NH3
Step 3: (Evaluate)
Because the molar mass of NH3 is substantially greather than the molar mass of H2, the answer should have a larger mass than the given mass. The answer should have two (2) significant figures.
More Practice Problems:
Other Stoichiometric Calculations: (page 363)
Zoey Killion
In any of these problems, the given quantity is first converted to moles. Then the mole ratio from the balanced equation is used to calculate the number of moles of the wanted substance. Finally, the moles are converted to any other unit of measurement related to the unit mole.
- aG (given quantity) -----> bW (wanted quantity)
Sample Problems 12.4: (page 364)Zoey Killion
Calculating the Molecules of a Product:
- Analyze: List the known and the unkown
- Calculate: Solve for the unknown.
- Evaluate: Does the result make sense?
Example:How many molecules of oxygen are produced when a sample of 29.2 g of water is decomposedby electrolysis, as shown in Figure 1? The balanced equation is:
2H20(l) ------> (electricity) 2H2 (g) + O2 (g)
Step 1: (Analyze)
Knowns:
- mass of water = 29.2 g H20
- 1 mol H20 = 18.0 g H20 (molar mass)
- 1 mol O2 = 6.02 X 10^23 molecules of O2
Unknown:- molescules of oxygen = ? molecules of O2
Step 2: (Calculate)2.92 g H2O X (1 mol H20/ 18.0 g H2O) X (1 mol O2/ 2 mol H2O) X (6.02 X 10^23 molecules of O2/ I mol O2) = 4.88 X 10^23 molecules O2
Step 3:
The given mass of water should produce a little less than 1 mol of oxygen, or a little less then Avogadro's number of molecules. The answer should have three (3) significant figures.
More Practice Problems:
- How many molecules of oxygen are produced by the decomposition of 6.54 g of potassium chlorate (KClO3)? 2KlO3(s) ---> 2KCl(s) + 3O2(g).
- The last step in the production of nitric acid is the reaction of nitrogen dioxide with water. 3NO2(g) + H2O(l) ----> 2HNO3(aq) + NO(g). How many grams of nitrogen dioxide must react with water to produce 5.00 X 10^22 molecules of nitrogen monoxide?
The coefficients in a chemical equation indicate the relative number of particles and the relative number of moles of reactants and products. For a reaction involving gaseous reactants or products, the coefficients also indicate relative amounts of each gas. As a result, you can use volume ratios in the same way you ahve used mole ratios.For more help with Stoichiometric Calculations watch this video:
http://www.youtube.com/watch?v=TGJARI7cXrU
Group 6 (Co-Editor Haley Conatser)
Mitch Martin and Dakota pg 368-371
. In a Chemical reaction, an insufficient quantity of any of the reactants will limit the amount of product that forms.
Limiting reagent: reagent that determines the amount of product that can be formed in a reaction.
Excess reagent: Not completely used up in the reaction.
Haley page 372-378