Chemical Reactions and Stoichiometry

The 7-H club

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) Reactants yields Products Physical state of substances

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 reaction So… the numbers of atoms must remain unchanged in a reaction

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)   2 1 1 1 Reactants Elements Products H Cl Zn

I. Parts of a Chemical Reaction and Balancing Examples: Balance the following chemical reactions _____ N2 + _____ H2  _____ NH3 2. _____ Al2O3  _____ Al + ____ O2 Complete 3 and 4 on your own.   Elements 1 3 2 Elements 2 4 3

I. Parts of a Chemical Reaction and Balancing Examples: Balance the following chemical reactions 3. _____ Al + _____ Br2  _____ AlBr3 4. _____ AlBr3 + ___ Cl2 _____ Al Cl3+ ____ Br2   Elements 2 3 2 2 Elements 2 3 3

II. Types of Reactions - Synthesis   What is it? General Equation: ________________________________ When two or more reactants combine to form a single product A + B  AB

Checks for Understanding   Real World Example: (video) Magnesium ribbon is heated and reacts with oxygen in the air forming magnesium oxide After 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)  2 1 2 Elements

II. Types of Reactions - Synthesis   C. Balancing: Balance the following synthesis reactions: 1. ____ S + ____ O2  ____ SO3 ____ C + ____ H2  ____ C3H8 Complete 3 and 4 on your own and then check with your partner Elements 2 3 2 3 4 1 Elements

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 . Iron and oxygen yields iron (III) oxide   4 3 2 ___ Fe + ___ O2  ___ Fe2O3

II. Types of Reactions - Synthesis Checks for Understanding 3. Practice: Write a balanced chemical reaction for each reaction described below Sulfur and oxygen Chromium and oxygen yields sulfur trioxide yields chromium (III) oxide 2 3 ___ S + ___ O2 4 3 ___ Cr + ___ O2 2  ___ SO3 2  ___ Cr2O3

III. Types of Reactions - Decomposition   What is it? General Equation: ________________________________ Single compound is broken down (decomposed) into two or more simpler substances AB  A + B

Checks for Understanding   Real World Example: (video) Hydrogen peroxide decomposes into water and oxygen After 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) 2 2 1 Elements

III. Types of Reactions - Decomposition   C. Balancing: Balance the following synthesis reactions: 1. ____ HgO  ____ Hg + ____ O2 ____ AgCl  ____ Ag + ____ Cl2 Complete 3 and 4 on your own and then check with your partner Elements 2 2 1 2 2 1 Elements

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   1 3 ___ NI3 2  ___ N2 + ___ I2

Checks for Understanding 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 ___ MgCl2 1 ___ Al2Cl3 2 1 1  ___ Mg + ___ CI2 4 3  ___ Al + ___ CI2

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 compound Reaction will only occur if the single element is more reactive than the element in the compound (see Table J) A + BX  B + AX

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  J The element by itself must be above (more reactive) in order for the reaction to occur below it LiCl + Na No reaction NaF + Cl2 (NOT BALANCED) No reaction

IV. Types of Reactions – Single Replacement   C. Balancing: Balance the following single replacement reactions: 1. ____ Cl2 + ____ KBr  ____ KCl + ____ Br2 ___ Fe + ____ AgC2H3O2  ___ Fe(C2H3O2)3 + ____ Ag ____ Li + _____ H(OH)  ___ LiOH + ___ H2 2 1 1 2 Elements K Cl Br 1 3 3 1 2 2 2 1

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  ____________________________ 1 1 1 ___ ZnSO4 +___ H2 1 No reaction (Pb is BELOW Fe) 2 2 1 ___ LiCl + ______ I2 1

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 chloride Potassium reacts with magnesium fluoride 3. Magnesium reacts with zinc nitrate 1 2 ___ Ca +___ NaCl  2 ___ CaCl2 +___ Na 1 2 ___ K +___ MgF2  2 1 ___ Mg+___ KF 1 1 1 1 1 ___ Mg+___ Zn(NO3)2  ___ Mg(NO3)2 +___ Zn

V. Types of Reactions – Double Replacement   A. What is it? Occurs only if a solid, gas, or water is formed Precipitates: See Table ____: Examples – Cu(NO3) _____ 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)

V. Types of Reactions – Double Replacement B. General Equation: VIDEO DEMOSTRATION AX + BY  BX + AY

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 2 1 1 s aq 1 Elements Ba Cl H SO4 1 3 1 3 s aq 1 1 2 1 aq aq l (s)

V. Types of Reactions – Double Replacement   D. Finish the Chemical Reaction: Balance the following reactions Write 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) _________________________________ 2 1 1 1 ___ NaNO3 (aq) +___ CdS (s) 1 1 1 2 ___ BaSO4 (s) +___ HCl (aq) 1 2 1 1 ___ BaCO3 (s) +___ KCl (aq)

V. Types of Reactions – Double Replacement   Chemical Reactions in Words: 1. Calcium Nitrate + Sodium Carbonate 2. Aluminum nitrate and sodium hydroxide 1 1 ___ Ca(NO3)2 (aq) +___ Na2CO3 (aq) 2 ___ CoCO3 (s) +___ NaNO3 (aq) 1 1 3 ___ Al(NO3)3 (aq) +___ NaOH (aq)  3 ___ Na(NO3) (aq)+___ Al(OH)3 (S) 1

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

VI. Types of Reactions – Combustion   Balancing: Balance the following reactions: ____ C4H12 + ____ O2  ____ H2O + ______ CO2 TRICKY!!! ____ CH3OH + ____ O2  ____ H2O + _____ CO2 _____ C2H6 + _____ O2  ______ H2O + _______ CO2 1 7 6 4 Elements C H O 3 4 2 2 2 5 6 4