Unit 2: Formula Writing, Naming Compounds, Equations, & Stoichiometry - PowerPoint Presentation

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Unit 2: Formula Writing, Naming Compounds, Equations, & Stoichiometry

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I. Percent Composition

Think about this:How would you find the percent of boys in our class? # of boys (part)____ x 100% Total # of students (whole)

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I. Percent Composition

Equation: (See Ref Tabs) Table ________Example 1: A 14.80 g sample contains 3.83 g of iron and 10.97 g of bromine. What is the percent composition of bromine?

Represents the composition as a percentage of each element compared with the total mass of the compoundT% Composition = mass of part * 100by mass mass of whole% Composition = mass of part * 100 = 10.97 g Br____ x 100 = 74.12 %by mass mass of whole 14.80 g Sample

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I. Percent Composition

Example 2: Find the percent by mass of nitrogen in NH4NO3.Example 3: Which species contains the greatest percent by mass of hydrogen? A) OH– B) H2O C) H3O- D) H2O2

Step 1: Find the GFM: 2 (14 g) + 4 (1 g) + 3 (16 g) = 80 gStep 2: % Composition = mass of part * 100 = 28 g N x 100 = 35 % by mass mass of whole 80 gA) 1/17 = 6 %B) 2/18 = 11 %C) 3/19 = 16 %D) 2/66 = 3 %

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II. Percent Hydrate

Think about this:A furry mole gets caught in a rain storm. His fur becomes wet and raises his mass to 125 g. He dries off and has a mass of 120 g. How would you find the percent of water that was on the wet mole?Difference in Masses of the Mole x 100%

Total Mass of Wet Mole5 g x 100% = 4% 125 g

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II. Percent Hydrate

Hydrate:Anhydrate:The water is NOT bonded to the compound. It is attracted by a molecule-ion force of attraction.Anhydrates can be used to absorb moisture in packaged electronic equipment and clothing. You have probably seen packages of sodium silicate (an anhydrate) used when buying a pair of shoes.

A compound that contains a specific amount of water molecules bound to its atomsA hydrate that has had the water driven off (evaporated)

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II. Percent Hydrate

Example 1: What is the percentage, by mass, of water in sodium carbonate crystals, Na2CO3 • 5H2O?

Step 1: Find the total GFM: 2(23g) + 1(12 g) + 3(16 g) + 10 (1g) + 5 (16 g) = 196 g Step 2: % Composition = Total mass of H2O* 100 = 5 (18 g) x 100 = 46% by mass GFM 196 g

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II. Percent Hydrate

Example 2: What is the percentage, by mass, of water in barium chloride crystals, BaCl2 • 2H2O?Example 3: Find the percent of water of hydration for CuSO4 • 5H2O.

% Composition = Total mass of H2O* 100 = 2 (18 g) x 100 = 15% by mass GFM 243 g % Composition = Total mass of H2O* 100 = 5 (18 g) x 100 = 36% by mass GFM 250 g

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II. Percent Hydrate

Example 4: A hydrate has a mass of 45.3g. After being heated to a constant mass, the substance has a mass of 39.8g. What is the percent water of hydration? Example 5: Given the lab data below, find the percent water of hydration.crucible 5.13 gcrucible and hydrate 7.14 gcrucible and anhydrate 6.29 g

Step 1: Find mass of H2O = 45.3 g – 39.8 g = 5.5 g of H2OStep 2: % Composition = mass of H2O* 100 = 5.5 g x 100 = 12% by mass Total mass 45.3 gStep 1: Find mass of hydrate = 7.14 g – 5.13 g = 2.01 g of hydrateStep 3: % Composition = mass of H2O* 100 = 0.85 g x 100 = 42% by mass Total mass 2.01 gStep 2: Find mass of water = 7.14 g – 6.29 g = 0.85 g of water

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II. Percent Hydrate (Practice)

Complete problems 4 and 6 from pg 15 (if you finish early, move on to problem 2 and 7)

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III. Writing Empirical Formulas

Empirical Formula:   – Examples: 1) BaCl2 2) CH4What is the empirical formula for C8H18?Molecular Formula: Only molecular compounds have molecular formulas – Example: C6H12O6

the simplest ratio in which atoms (moles) combine to form a compound Ionic compounds are ALWAYS written as empirical formulas (most reduced)C4H9 the actual ratio of the atoms (moles) in a molecule (NO IONIC COMPOUNDS)Molecular compounds have only COVALENT BONDS

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IV. Finding an Empirical Formula Given % Composition

Given: 11.1% H and 88.9% O, find the empirical formulaSteps1. Convert % to grams (assuming 100 g sample)2. Convert grams to moles (Divide by gam)3. Divide the moles by the SMALLEST # of moles to get ratio4. Write formula

11.1 % H  11.1 g H88.8% O  88.9 g O11.1 g H x 1 mol H = 11.1 mol H 1 g H88.9 g O x 1 mol O = 5.5 mol O 16 g O11.1 mol H = 2 mol H 5.56 5.56 mol O = 1 mol O 5.56 H

2O

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IV. Finding an Empirical Formula Given % Composition

Examples: Find the empirical formulas for the following problems.69.6 % barium, 6.1 % carbon, 24.3% oxygen40.5% zinc, 19.9 % sulfur, 39.6% oxygen

69.9 g Ba x 1 mol Ba = 0.508 mol Ba 137 g Ba6.1 g C x 1 mol C = 0.508 mol C 12g C24.3 g O x 1 mol O = 1.52 mol O 16 g O0.508 mol Ba = 1 mol Ba 0.5080.508 mol C = 1 mol C 0.5081.52 mol O = 3 mol O

0.508BaCO340.5 g Zn x 1 mol Zn = 0.623 mol Zn 65 g Zn19.9 g S x 1 mol S = 0.622 mol S 65 g S39.6 g O x 1 mol O = 2.48 mol O 16 g O0.623 mol Zn = 1 mol Zn0.6230.622 mol S = 1 mol S0.6232.48 mol O = 4 mol O0.623

ZnSO

4

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IV. Finding an Empirical Formula Given % Composition

If you don’t end up within a tenth of a whole number, multiply both numbers by 2 to get whole number ratioExample - A compound of zinc and phosphorous, when analyzed, showed 76.0% Zn and 24.0% P by mass. Calculate the simplest formula for the compound.76.0 g Zn x

1 mol Zn = 1.17 mol Zn 65 g Zn24.0 g P x 1 mol P = 0.774 mol P 31 g P1.17 mol Zn= 1.5 mol Zn0.774 0.774 mol P = 1 mol P0.774Zn3P2* 2 = 3 Zn* 2 = 2 P

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V. Finding a Molecular Formula

What is the molecular formula of a compound that has a GFM of 92 g and an empirical formula of NO2?Steps1. Find the empirical formulaFind the mass of the empirical formula Find how many times larger the GFM is than the empirical formula and multiply the subscripts by that number.

NO21 (14 g) + 2 (16 g) = 46 g92 g/ 46 g = 2 times larger than the empirical formulasN2O4

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V. Finding a Molecular Formula

Example:1. A compound of phosphorus and oxygen, when analyzed, showed 39.24% P and 60.76% O by mass. Calculate the simplest formula for the compound.2. Find the molecular formula if the GFM of this compound is 158g.

39.24 g P x 1 mol P = 1.27 mol P 31 g P60.76 g O x 1 mol O = 3.80 mol O 16 g O1.27 mol P = 1 mol P1.273.80 mol O = 3 mol O 1.27PO31 (31 g) + 3 (16 g) = 79 g158 g/ 79 g = 2 times larger than the empirical formulasP2

O6

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Comparing Molecular vs. Empirical Formulas

Empirical Formula: Summarize what an empirical formula is.Molecular Formula: Summarize what a molecular formula is.Actual ratio of atoms (moles) in a

moleculeSimplest ratio which atoms combine to form a compound

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Molecular Formula vs. Covalent Formulas C

2H2 Ca3N2 SCl3 C8H81. Identify the empirical formulas: ______________________________________________2. A) Identify the molecular formulas: ___________________________________________ B) What is the empirical formula of these substances? _______________________  C) Why would these substances have different chemical properties?Empirical formulas involve what types of bonding? _____________________________4. Molecular formulas involve what type of bonding? ______________________________

Ca3N2 SCl3C2H2 C8H8CHThe molecular formula indicates how many atoms are bonded. The way and number of bonds affect the properties.

Ionic and covalentCovalent only

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Practice Problems

: Show your work on the whiteboard and call Mrs. Pelc over once your group has completed the entire problem. Be sure to show all work for each problem.1. A compound has an empirical formula Al2O3.A)Why does this compound not have a molecular formula?B) Calculate the percent composition of each element. 2. A substance has a formula of C8H18.A) What is the empirical formula of this substance?B) Using the empirical formula, calculate the percent composition of each element?  3. A substance contains 30.4% N and 69.6% O.A) Calculate the empirical formula of the compound (show all work).

B) If the compound has a gram formula mass of 92 g, what is the molecular formula of the substance? 4. A hydrate consists of 19.17 % Na, 13.33 % S, and 67.50 % H2O.A) Calculate the empirical formula of the hydrate (show all work). B) Why does this hydrate not have a molecular formula?

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VI. Naming Compounds

2. Good conductors of heat and electricity3. Exhibit metallic luster (shine)1. Low ionization energy and electronegativity4. Malleability (can be pounded into thin sheets)5. Ductility (can be pulled into thin wires)6. More than 2/3 of the elements are metals Atoms that ______ and form ________

____ _________ when bonding Alloy:Mixture of metals by melting them togetherlose e-positive ions(cations) Properties of Metals:Metals:

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7.

_____ densities. 8. ____________ is a metal which is a ______ at room temperature.9. Most active metal: _____________HighMercury (Hg)liquidFr (francium)

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Properties of Nonmetals:2. Poor conductors of heat and electricity3. Brittle and hard1. High ionization energy and electronegativity4. Low densities5. Most active nonmetal: ________F (Fluorine) (top right corner)Graphite is an allotrope of carbon. It is used in pencils (brittle, soft, and low density)

atoms gain e- and form negative ions (anions) when bondingNonmetals:

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Metalloids

Atoms that gain or lose e- and form ions when bonding Have properties of both metals and nonmetals Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium

Can be located using the “

staircase

” (see periodic table)

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Writing Formulas of Binary Ionic Bonds

Assigning Oxidation NumbersOxidation number tells you how many electrons are involved in bondingThe sum of the oxidation numbers for a compound must equal zeroFor elements with multiple oxidation numbers, that is just SOME of the possible oxidation numbersFor nonmetals, use the first negative charge listed

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Writing Formulas of Binary Ionic Bonds

Criss-Cross Method: Use to find how many ions of each element are involved in a bond. Check to see the sum of the oxidation numbers equals zero.Examples: Cu 2+ with N 3 - Co 3+ and Sulfate (SO4) 2 - Cu3N23(+2) + 2(-3) = 0Co2(SO4)32(+3) + 3 (-2) = 0

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Writing Formulas of Binary Ionic Bonds

Check for understanding: Write the formula for the following ions with their charges. Check to see the sum of the oxidation numbers equals zero.A) Na 1+ and P 3 - C) Al 3+ and N 3 -B) Cr 3 + and S 2 - D) Ca 2+ and SO3 2 - Na3P3(+1) + 1(-3) = 0Cr2S32(+3) + 3(-2) = 0Al

3N3  AlN1(+3) + 1(-3) = 0Ca2(SO3)2  Ca(SO3)1(+2) + 1(-2) = 0

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Naming Formulas of Binary Ionic Bonds

Nonmetal’s names change when forming ionic bondsNitrogen  NitridePhosphorus  PhosphideSulfur  SulfideOxygen  OxideChlorine  ChlorideFluorine  FluorideBromine  BromideIodine  IodideCarbon  CarbideHydrogen  Hydride -

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Naming Formulas of Binary Ionic Bonds

A) Naming Binary Ionic Compounds (contains a metal and a nonmetal)Examples: A) ZnO C) KCl B) Ag2S D) Al2Br3 - Name of the metal plus name of the nonmetal- The negative ion (if a nonmetal) ending changes to -ide (for polyatomic ions just write the name)

Zinc OxygenZinc OxideSilver SulfurSilver SulfidePotassium ChlorinePotassium ChlorideAluminum BromineAluminum Bromide

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Naming Formulas of Ternary Ionic Bonds

B) Naming Ternary Ionic Compounds (contain a metal with a Polyatomic Ion (PI))- Name the metal plus the name of the polyatomic ion (PI)Examples: A) Zn(OH)2 C) GaPO4 B) AgCN D) Mg(ClO3)2 Zinc HydroxideSilver Cyanide Gallium Phosphate

Magnesium Chlorate

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Naming Formulas of Ternary Ionic Bonds

C) Naming Ionic Compounds with Roman Numerals (contain a metal with multiple oxidation numbers) Use the reverse criss-cross method to identify the charge of the ions. If the positive ion has more than one listed charge (transition metals), use a Roman numeral after the metal’s name to indicate the charge (you do NOT use a Roman numeral for the nonmetal/PI) If there is a 1-1 ratio between the metal and negative ion, the charge of the metal will have the same charge of the negative ion (nonmetal/polyatomic ion)

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Naming Formulas of Ternary Ionic Bonds

Examples:A) Cr2O3 C) FeCl3B) CrO D) NiPO4 Chromium (III) OxideChromium (II) OxideIron (III) ChlorideNickel (III) Phosphate

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Writing Formulas of Ionic Bonds

A) Writing Binary Ionic Compounds (contain a metal and nonmetal) Write the symbols for the metal and nonmetal. Look up the charges (oxidation numbers) for each of the ions. For the nonmetal, it is the first negative number listed. Criss-cross the charges to get the number of ions used for each element and drop the +/-- Reduce to the smallest ratio, if you can.

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Writing Formulas of Ionic Bonds

Examples:A) Sodium Sulfide C) Aluminum OxideB) Magnesium Fluoride D) Calcium Oxide Na2SMgF2Al2O3CaONa1+

S2- Mg2+F1- Al 3+O 2- 

Ca +2O2- 

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Writing Formulas of Ionic Bonds

B) Writing Ternary Ionic Compounds (contain a metal with a PI ) Write the symbols for the metal and PI. Look up the charges (oxidation numbers) for each of the ions. Criss-cross the charges to get the number of ions used for each element/PI and drop the +/-- Reduce to the smallest ratio, if you can.

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Writing Formulas of Ionic Bonds

Examples:A) Calcium Hydroxide C) Aluminum PhosphateB) Zinc Phosphate D) Rubidium Chromate Ca(OH)2Zn3(PO4)2AlPO4Rb2(CrO4)

Ca 2+OH 1- Zn 2+PO43- Al 3+

PO43- Rb 1+CrO42- 

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Writing Formulas of Ionic Bonds

C) Writing Ionic Compounds with Roman Numerals (contain a metal with multiple oxidation numbers) Write the symbols for the metal and nonmetal/PI. If a Roman numeral is in the name, it represents the charge of the METAL. For the nonmetal, use the first negative charge listed. Criss-cross the charges to get the number of ions used for each element/PI and drop the +/-- Reduce to the smallest ratio, if you can.

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Writing Formulas of Ionic Bonds

Examples:A) Iron (III) Oxide C) Nickel (III) Phosphate   B) Manganese (II) Fluoride D) Manganese (IV) Chromate Fe2O3MnF2NiPO4Mn2(CrO4)4

(REDUCE)Fe 3+O 2- Mn 2+ F 1- 

Ni 3+PO43- Mn 4+CrO42- Mn

(CrO

4

)

2

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Naming Formulas of Molecular Compounds (Molecules)

 Examples:A) NO C) P2O5B) PF5 D) N2O3 One with the SMALLER electronegativity gets named FIRST Always use a prefix for the SECOND element and change the ending to

-ide If the first element has more than one atom, use a PREFIX. Nitrogen MonoxidePhosphorous PentafluorideDiphosphorous PentoxideDinitrogen

Trioxide

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Naming acids and bases

Naming Binary Acids (hydrogen with nonmetal):- Name the hydrogen in the acid hydro-- Name the anion and change ending of the name to –ic acidExamples:1. HCl (aq) - ____________________________2. HI (aq) - __________________________3. HBr(aq) - ____________________________4. H2S(aq) - _____________________________Hydrochloric acidHydroiodic acid

Hydrobromic acidHydrosulfuric acid

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Naming acids and bases

Naming Ternary Acids (hydrogen with PI’s) Go to Table ______ and name the PI (polyatomic ion)DO NOT use the prefix hydro –If the PI ends in - ate, it changes to –ic acidIf the PI ends in – ite, it changes to –ous acidExamples:1) H2CO3 (aq) - _ ____________________________2) H3PO4 (aq) - _____________________________3) H2SO4 (aq) - _____________________________4) H2SO3(aq) - _____________________________E

Carbonic acidPhosphoric acidSulfuric acidSulfurous acid

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Naming acids and bases

Naming Bases:- Bases are all ____________________, therefore, they are named just like ________________Name 1st elementUse roman numeral if the metal has more than one charge listed2nd half of the name will typically be _______________Examples:1. NaOH (aq) - ____________________IONIC COMPOUNDSIONIC COMPOUNDSSodium hydroxideHYDROXIDE

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Naming acids and bases

Naming Bases (continued):2. Ca(OH)2 (aq) - _____________________________3. Fe(OH)3 (aq) - _____________________________4. Co(OH)2 (aq) - _____________________________Calcium hydroxideIron (III) hydroxideCobalt (II) hydroxide

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Naming Formulas of Ternary Molecular Compounds (Molecules with PI) 

1. A polyatomic ion contains two or more elements bonded together with a __________. See Table E.2. Name the __________ and then the polyatomic ion.Practice Naming Compounds with Polyatomic Ions1. Name the following. Use Roman Numeral when necessary.

____________________ NH4Cl ____________________ NaNO3____________________ CaCO3 ____________________ Fe(ClO3)3

____________________ Mg(HCO3)2 ____________________ ZnSO42. Write formulas for the following. Balance the charges of the metal and polyatomic ion. _______________ potassium oxalate

_______________

gold (III) chlorate

_______________

sodium thiosulfate

______________

copper (II) hydroxide

charge

metal

a

mmonium chloride

s

odium nitrate

c

alcium carbonate

i

ron (III) chlorate

magnesium hydrogen carbonate

zinc sulfate

K

2

C

2

O

4

Au(ClO

3

)

3

Na

2

S

2

O

3

Cu(OH)

2

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Unit 2:Balancing Chemical Equations

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I. Parts of a Chemical Reaction and Balancing

What is a chemical reaction? Example: (video) HCl (aq) + Zn (s)  H2(g) + ZnCl2(aq) (NOT BALANCED)One or more substances are made into NEW substance(s) (bonds are broken and/or made)ReactantsyieldsProductsPhysical state of substances

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I. Parts of a Chemical Reaction and Balancing

Example: HCl (aq) + Zn (s)  H2(g) + ZnCl2(aq) (NOT BALANCED)  Problem: The above chemical reaction breaks the Law of Conservation of Mass:Matter is neither created or destroyed in a chemical reactionSo… the numbers of atoms must remain unchanged in a reaction

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I. Parts of a Chemical Reaction and Balancing

Balancing Equations: Coefficients are used to balance the number of at atoms of each element on both sides of the reaction. Coefficients must be the smallest whole number that balance the reaction. NOTE: Coefficients can be changed, HOWEVER, subscripts CANNOT!Example: ____ HCl (aq) + ____ Zn (s)  ____ H2(g) + ____ ZnCl2(aq) Reactants

ElementsProductsH

Cl

Zn

2

1

1

1

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I. Parts of a Chemical Reaction and Balancing

Examples: Balance the following chemical reactions_____ N2 + _____ H2  _____ NH3 2. _____ Al2O3  _____ Al + ____ O2Complete 3 and 4 on your own. 

Elements

Elements

1

3

2

2

4

3

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I. Parts of a Chemical Reaction and Balancing

Examples: Balance the following chemical reactions3. _____ Al + _____ Br2  _____ AlBr3 4. _____ AlBr3 + ___ Cl2 _____ Al Cl3+ ____ Br2 

Elements

Elements

2

3

2

2

3

2

3

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II. Types of Reactions - Synthesis

 What is it? General Equation: ________________________________When two or more reactants combine to form a single productA + B  AB

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Checks for Understanding

 Real World Example: (video)Magnesium ribbon is heated and reacts with oxygen in the air forming magnesium oxideAfter watching the demonstration, what are some observations you made that proved that a chemical reaction occurred? Balance the following chemical reaction____ Mg (s) + ____ O2 (g)  ____ MgO (s) 

Elements

2

1

2

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II. Types of Reactions - Synthesis

 C. Balancing: Balance the following synthesis reactions:1. ____ S + ____ O2  ____ SO3 ____ C + ____ H2  ____ C3H8Complete 3 and 4 on your own and then check with your partner

Elements

Elements

2

3

2

3

4

1

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II. Types of Reactions - Synthesis

D. Chemical Reactions in Words: Write and balance the following equations. Remember to criss-cross and pay attention to diatomic elements (7 - H club).Iron and oxygen yields iron (III) oxide ___ Fe+ ___ O2 ___ Fe2O3

432

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II. Types of Reactions - Synthesis

 Checks for Understanding3. Practice: Write a balanced chemical reaction for each reaction described below  Sulfur and oxygen Chromium and oxygen yields sulfur trioxide yields chromium (III) oxide ___ S+ ___ O2 ___ SO32

32___ Cr+ ___ O2 ___ Cr2O343

2

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III. Types of Reactions - Decomposition

 What is it? General Equation: ________________________________Single compound is broken down (decomposed) into two or more simpler substancesAB  A + B

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Checks for Understanding

 Real World Example: (video)Hydrogen peroxide decomposes into water and oxygenAfter watching the demonstration, what are some observations you made that proved that a chemical reaction occurred? Balance the following chemical reaction____ H2O2 (l)  ____ H2O (l) + ______ O2 (g)

Elements

2

2

1

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III. Types of Reactions - Decomposition

 C. Balancing: Balance the following synthesis reactions:1. ____ HgO  ____ Hg + ____ O2____ AgCl  ____ Ag + ____ Cl2Complete 3 and 4 on your own and then check with your partner

Elements

Elements

2

2

1

2

2

1

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III. Types of Reactions - Decomposition

D. Chemical Reactions in Words: Write and balance the following equations. Remember to criss-cross and pay attention to diatomic elements (7 - H club).Nitrogen Triiodine decomposes to nitrogen and iodine ___ NI3 ___ N2+ ___ I2

213

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 3. Practice: Write a balanced chemical reaction for each reaction described below

  Magnesium chloride decomposes Aluminum oxide decomposes into magnesium and chlorine  into aluminum and oxygen Checks for Understanding___ MgCl2 ___ Mg+ ___ CI21

11___ Al2Cl3 ___ Al+ ___ CI22

43

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IV. Types of Reactions – Single Replacement

 A. What is it? B. General Equation: 2K (s) + 2H(OH) (l)  H2 (g) + 2KOH (aq)Atoms of one element replace the atoms of a second element in a compound (metal switches with metal or nonmetal switches with nonmetal)

Always involves an element and a compoundReaction will only occur if the single element is more reactive than the element in the compound (see Table J)A + BX  B + AX

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IV. Types of Reactions – Single Replacement

 See Table _____ to verify if reaction will occur ***A metal/nonmetal will replace any metal/nonmetal listed _________Example: NaCl + Li  NaCl + Mg  NaCl + F2  NaF + Cl2 

JThe element by itself must be above (more reactive) in order for the reaction to occur below itLiCl + NaNo reactionNaF + Cl2 (NOT BALANCED)No reaction

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IV. Types of Reactions – Single Replacement

 C. Balancing: Balance the following synthesis reactions: 1. ____ Cl2 + ____ KBr  ____ KCl + ____ Br2___ Fe + ____ AgC2H3O2  ___ Fe(C2H3O2)3 + ____ Ag

____ Li + _____ H(OH)  ___ LiOH + ___ H2 2211

Elements

K

Cl

Br

1

3

1

3

2

2

2

1

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IV. Types of Reactions – Single Replacement

 D. Finish the Chemical Reaction:Use Table J to see if the following reactions can occur. If it can, write the product and balance the equation (if necessary). Remember to criss-cross and pay attention to diatomic elements (7 - H club).____ Zn + ____ H2SO4  _______________________________Pb + _____ FeCl3  _______________________________ Cl2 + _____ LiI  ____________________________ ___ ZnSO4 +___ H2

1111No reaction (Pb is BELOW Fe)___ LiCl + ______ I21221

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IV. Types of Reactions – Single Replacement

 D. Chemical Reactions in Words: Write and balance the following equations. Use Table J to see if the following reactions can occur. If it can, write the product and balance the equation (if necessary). Remember to criss-cross and pay attention to diatomic elements (7 - H club).1. Calcium reacts with Sodium chloridePotassium reacts with magnesium fluoride3. Magnesium reacts with zinc nitrate ___ Ca +___ NaCl ___ CaCl2 +___ Na12

12___ K +___ MgF2 ___ Mg+___ KF2112___ Mg+___ Zn(NO3)2

___ Mg(NO3)2 +___ Zn1111

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V. Types of Reactions – Double Replacement

 A. What is it? Occurs only if a solid, gas, or water is formedPrecipitates: See Table ____: Examples – CuNO3 _____ Ca3(PO4)2 ____ PbCl2 ______ Ba(OH)2 ____Involves an exchange of positive ions between two reacting ionic compounds

A solid formed as a product of a reaction that does not dissolve in water (insoluble)F(aq)(s)(s)(aq)

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V. Types of Reactions – Double Replacement

B. General Equation: VIDEO DEMOSTRATIONAX + BY  BX + AY

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V. Types of Reactions – Double Replacement

 C. Balancing: Balance the following reactions____ BaCl2 (aq) + ____ H2SO4 (aq)  ____ BaSO4 ( ) + _____ HCl ( ) ____ Al(NO3)3 (aq) + ___ NaOH (aq)  ____ Al(OH)3 ( )+ _____ NaNO3 ( )

____ Ca(OH)2 ( ) + ____ H2SO4 ( )  ____ HOH ( ) + ____ CaSO4 Elements

Ba

Cl

H

SO

4

s

aq

1

1

1

2

s

aq

1

3

1

3

aq

aq

l

(s)

1

1

2

1

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V. Types of Reactions – Double Replacement

 D. Finish the Chemical Reaction: Balance the following reactionsWrite the products and balance the equation (if necessary). Remember to criss-cross.____ Na2S (aq) + _____ Cd(NO3)2 (aq)  ___________________________________BaCl2 (aq) + ____ H2SO4 (aq)  ___________________________________________ BaCl2 (aq) + _____ K2CO3 (aq) _________________________________

___ NaNO3 (aq) +___ CdS (s)1121___ BaSO4 (s) +___ HCl (aq)11

12___ BaCO3 (s) +___ KCl (aq)1112

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V. Types of Reactions – Double Replacement

 Chemical Reactions in Words: 1. Calcium Nitrate + Sodium Carbonate2. Aluminum nitrate and sodium hydroxide ___ Ca(NO3)2 (aq) +___ Na2CO3 (aq)___ CaCO3 (s) +___ NaNO3 (aq)1

112___ Al(NO3)3 (aq) +___ NaOH (aq) ___ Na(NO3) (aq)+___ Al(OH)3 (S)13

31

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VI. Types of Reactions – Combustion

 A. What is it? General Equation (VIDEO – Combustion of Methane (g)):An organic compound (consists of C and H) reacts with oxygen and creates ONLY carbon dioxide (CO2) and water (H2O)Organic Compound + O2

 H2O + CO2

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VI. Types of Reactions – Combustion

 Balancing: Balance the following reactions:____ C4H12 + ____ O2  ____ H2O + ______ CO2TRICKY!!! _____ C2H6 + _____ O2  ______ H2O + _______ CO2_____ CH3OH + ______ O2  ______ H

2O + ______CO2Elements

C

H

O

1

7

6

4

2

7

6

4

2

3

4

2

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VIII. Stoichiometry

Applying math to chemical equationsReasons: 1. To find the perfect “recipe” of reactants, producing the most products 2. To predict the mass or volume of every reactant and productCoefficients:

Tell you how many moles of the compound or element there are

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VIII. Stoichiometry

Think about this:The “recipe” for bread is: 3 cups of flour + 1 eggs  4 loafs of bread1) How many loafs of bread is produced if you use 6 cups of flour?2) How many eggs are needed to produce 12 loafs of bread?

8 loafs3 eggs

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VIII. Stoichiometry

Mole – Mole Problems: Using moles means using coefficientsExample 1: _____ H2 + ____ O2  ____ H2OHow many moles of each of the substances? ____ H2 ____ O2 ____ H2OWhat is the mole ratio of O2 to H2?If I want to burn 5 moles of O2, how many moles of H2 gas is needed?

212212

1 mol O2 : 2 mol H25 mol O2 x 2 mol H2 1 mol O2 = 10 mol H2

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VIII. Stoichiometry

Example 2: How many moles of ammonia (NH3) are produced when 0.60 mole of nitrogen reacts with hydrogen? (first balance)_____ N2 + ____ H2  ____ NH3Example 3: How many moles of aluminum are needed to form 3.7 mol of Al2O3? (first balance)_____ Al (s) + ____ O2 (g)  ____ Al2O3 (s)

0.60 mol N2 x 2 mol NH3= 1.2 mol NH3 1 mol N2 132

3.7 mol Al2O3 x 4 mol Al = 7.4 mol Al 2 mol Al2O3 432

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Honors ChemistryMass-Mass Problems

: When the mass of one substance in a reaction is given and you are asked to determine the mass of another substance in the reaction. The key to solving a mass-mass problem is having a correctly balanced equation.Example: How many grams of NaCl must be decomposed to yield 355 grams of Cl2?Write the balanced equation, given, and unknown.  

    Convert given to moles.

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Honors Chemistry

3. Find moles of unknown using mole ratios from balanced equation.      

 4. Find mass of unknown.      

Same problem in 1 step using factor-label (dimensional analysis) method.

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Honors ChemistryMass-Volume Problems

: When the mass or volume of one substance in a reaction is given and you are asked to determine the mass or volume of another substance in the reaction. The key to solving a mass-volume problem is having a correctly balanced equation.Example: In the reaction, Zn + 2HCl → ZnCl2 + H2, what volume of hydrogen is produced, at STP, when 3.27g of zinc are reacted with excess hydrochloric acid? Write the balanced equation, given, and unknown.  

    Convert given to moles.

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Honors Chemistry

3. Find moles of unknown using mole ratios from balanced equation.4. Find volume of unknown using molar volume.Volume-Volume Problems: As you can imagine, these problems are very similar to mass-mass problems.Example: In the reaction, 2C

2H6 + 7O2 → 4CO2 + 6H2O, how many liters of oxygen are required for the complete combustion of 15.6L of ethane (C2H6)?

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Honors Chemistry Given

, N2(g) + 3H2(g) → 2NH3(g), Before reaction: Limiting and Excess Reagents: In a chemical reaction, an insufficient quantity of any of the reactants will limit the amount of product that forms. Limiting reagent: reagent is used up and determines amount of product that can be formed.Excess reagent: not completely used up; some remains unreacted.

2 molecules N23 molecules H2

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Honors Chemistry

After reaction: 1 molecule N2 (excess reagent) 0 molecules H2

2 molecules NH3(limiting reagent) (product)Determining the Limiting Reagent in a Reaction: Given: 2Cu (s) + S(s) → Cu2S(s), what is the limiting reagent when 80.0g Cu reacts with 25.0g S?

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Honors Chemistry

Using a Limiting Reagent to Find the Quantity of a Product Given, 2Cu (s) + S(s) → Cu2S(s), what is the maximum number of grams of Cu2S that can be formed when 80.0g Cu reacts with 25.0g S?