CHEMICAL REACTIONS & EQUATIONS

Chemical Reactions

Chemical Reactions Process in which one or more substances are converted into new substances with different physical and chemical properties For example, a yellow solid precipitate, lead iodide (PbI2), forms from the mixture of two clear liquids, potassium iodide (KI) and lead nitrate (Pb(NO3)2).

Word Equation Hydrogen + Oxygen Water + Energy Reactants Products

Balanced Formula Equations 2 H2 (g) + O2 (g) 1 2 H2O (l) Why? To give a quantitative, as well as qualitative information.

2H2 (g) + 1O2 (g) 2H2O (l) 2 Molecules Water 2 Molecules H + 1 molecule O + 2 Moles H2 + 1 Mole O2 2 Moles Water 4 g 32 g + 36 g

Rules for Balancing Equations 1. Write correct formulas for all reactants and products. Use the symbols for elements: Iron = Fe Don’t forget diatomic elements travel in pairs! H2, N2, O2, F2, Cl2, Br2, I2

Rules for Balancing Equations 2. Obey the LAW OF CONSERVATION OF MASS. Same number of each kind of atom on both sides of the equation. 25g + 25g + 50 g 50 g + 150 g ?g

How to Balance an Equation 3. To balance atoms of reactants and products, change ONLY the coefficients. 4. Do NOT change the chemical formula to balance numbers of atoms. Numbers IN FRONT of the formulas NOTE: Subscripts are lower numbers in formula 4 Al2O3 Coefficient Subscripts

How to Balance an Equation cont. 5. Check your work by counting atoms of each element. 6. Check to see that the coefficients are in the lowest whole number ratio. 2H2O (l) 2H2 (g) + 1O2 (g) 4 Hydrogen 4 Hydrogen 2 Oxygen 2 Oxygen

Practice Balancing These Equations Ca + O2 CaO 2 1 2 1 Ca 1 Ca 2 O 1 O *Hint: Start by making the uneven side even. 2 O 2 O 1 Ca 2 Ca 2 Ca 2 Ca 2 O 2 O 2 Ca, 2 O 2 Ca, 2 O

Practice 1 2 1 2 CH4 + O2 CO2 + H2O 2 O 3 O 4 O 4 O 1 C 1 C 4 H 4 H *Hint: Start with the element that is split up: Oxygen. Then, make uneven side even. 2 O 3 O 4 O 4 O 1 C 1 C 4 H 4 H 1 C, 4 H, 4 O 1 C, 4 H, 4 O

Practice Fe + Cl2 FeCl3 2 1 3 2 1 Fe 1 Fe 2 Cl 3 Cl 6 Cl 6 Cl 1 Fe

Practice 2 HgO Hg + O2 2 1 1 3 2 Al + MnO Al2O3 + Mn 3 2 Al, 3 Mn, 3 O Br2+ NaI NaBr + I2 1 2 2 Br, 2 Na, 2 I 2 Br, 2 Na, 2 I Do these on own 2 HgO Hg + O2 2 1 2 Hg, 2 O 2 Hg, 2 O

Coefficients Must Be in Lowest WHOLE Number! 2 2 2 5 4 1 21/2 1 C2H2 + O2 CO2 + H2O What number can you multiply 21/2 by to get the smallest whole number? 2! So, multiply the whole equation by 2 to get a properly balanced equation. 4 C, 4 H, 10 O 4 C, 4 H, 10 O

You try. Multiply by 2! 8 C, 2O H, 26 O 8 C, 2O H, 26 O 1 13 61/2 8 4 10 5 C4H10 + O2 CO2 + H2O 2 Multiply by 2! 8 C, 2O H, 26 O 8 C, 2O H, 26 O

Classification of Chemical Reactions 1. Synthesis 2. Decomposition 3. Single Replacement 4. Double Replacement 5. Combustion (burning)

A B AB Synthesis Examples: 1 2 Cu + O2 CuO 1 H2CO3 CO2 + H2O Two reactants combine to form a single product (compound). A B AB One Product Examples: 1 2 Cu + O2 CuO 1 H2CO3 CO2 + H2O

AB A B Decomposition Examples: 2 3 KClO3 KCl + O2 1 2 H2O2 H2O + O2 One reactant breaks down to form two or more products. AB A B One Reactant Examples: 2 3 KClO3 KCl + O2 1 2 H2O2 H2O + O2

A BC AC B Single Replacement Examples: 2 1 Mg + HCl MgCl2 + H2 2 1 One element replaces another from a compound A BC AC B Examples: 2 1 Mg + HCl MgCl2 + H2 2 1 Cl2 + KI KCl + I2

Double Replacement (ionic) Ions in a solution combine to form a product that leaves the scene of the reaction AB CD AD CB Example: AgNO3 (aq) + NaCl (aq) AgCl (s) + NaNO3 (aq)

More on Double Replacement Precipitate (s), gas (g) or water (H2O) will form AgNO3 (aq) + NaCl (aq) AgCl (s) + NaNO3 (aq) Actual reaction: AgCl Ag+1 + Cl-1 Don’t dwell (do it in depth later) Spectator Ions: Na+1 & NO3-1

What happens when you put AgNO3 and NaCl in water? AgNO3 (aq) + NaCl(aq) AgCl(s) + NaNO3(aq) AgNO3 (aq) + NaCl(aq) AgCl(s) + NaNO3(aq) What happens when you put AgNO3 and NaCl in water? What happens when you put AgNO3 and NaCl in water?

NaCl AgNO3

NaCl AgNO3

AgNO3 NaCl

AgNO3 NaCl

AgNO3 NaCl

AgNO3 NaCl

AgNO3 NaCl

Ag NO3 Na Cl

Ag+ NO3- Na+ Cl-

Ag+ NO3- Na+ Cl-

Ag+ NO3- Cl- Na+

NO3- Ag+ Na+ Cl-

NO3- Na+ Ag+ Cl-

NO3- Na+ Ag+ Cl-

NO3- Na+ Cl- Ag+

Na+ NO3- Cl- Ag+

Na+ NO3- Cl- Ag+

Na+ NO3- Ag+ Cl-

Na+ NO3- Ag+ Cl-

Na+ NO3- Ag+ Cl-

Na+ NO3- Ag+ Cl-

NO3- Na+ AgCl

Na+ NO3- AgCl

Na+ NO3- AgCl

Na+ NO3- AgCl(s) precipitate AgCl

Na+ NO3- AgCl(s) precipitate AgCl

Na+ NO3- AgCl

NO3- Na+ AgCl

NO3- Na+ AgCl

Na+ NO3- AgCl

Na+ NO3- AgCl

Na+ NO3- AgCl

Na+ NO3- AgCl

Na+ NO3- AgCl

Na+ NO3- AgCl

AgNO3 NaCl NaCl NaCl AgNO3 AgNO3 NaCl NaCl NaCl AgNO3 AgNO3 AgNO3 AgNO3 NaCl

AgNO3 NaCl NaCl NaCl AgNO3 AgNO3 NaCl NaCl NaCl AgNO3 AgNO3 AgNO3 AgNO3 NaCl

AgNO3 NaCl NaCl NaCl AgNO3 AgNO3 NaCl NaCl NaCl AgNO3 AgNO3 AgNO3 AgNO3 NaCl

AgNO3 NaCl NaCl NaCl AgNO3 AgNO3 NaCl NaCl NaCl AgNO3 AgNO3 AgNO3 AgNO3 NaCl Ag+ Na+ NO3- Cl-

AgNO3 NaCl NaCl NaCl AgNO3 NaCl AgNO3 Ag+ Na+ NO3- Cl- Ag+ Cl- NO3- Na+ Na+ Ag+ NO3- Cl- AgCl

Ag+ Na+ NO3- Cl- Cl- Cl- Na+ Ag+ NO3- NO3- Ag+ Na+ NO3- Ag+ Cl- Na+ NO3- Cl- NO3- Na+ Cl- Na+ Ag+ Ag+ Cl- Ag+ Cl- Cl- Ag+ Ag+ AgCl AgCl AgCl

Ag+ NO3- Cl- Ag+ NO3- Na+ Ag+ Cl- NO3- Na+ NO3- Ag+ Cl- NO3- NO3- Na+ Cl- Na+ Na+ Cl- Ag+ Ag+ Na+ NO3- Cl- NO3- Na+ Na+ Na+ Cl- Ag+ AgCl AgCl AgCl AgCl

Ag+ NO3- Cl- NO3- Na+ NO3- NO3- Na+ Ag+ NO3- NO3- Cl- Na+ Na+ Na+ Cl- Ag+ Ag+ NO3- Cl- Na+ Na+ Na+ NO3- Na+

NO3- NO3- Na+ NO3- NO3- Na+ NO3- NO3- Na+ Na+ Na+ Cl- Ag+ Ag+ NO3- Cl- Na+ Na+ Na+ NO3- Na+

NO3- NO3- Na+ NO3- NO3- Na+ NO3- NO3- Na+ Na+ Na+ Cl- Ag+ Ag+ NO3- Cl- Na+ Na+ Na+ NO3- Na+

NO3- Na+ Na+ NO3- Na+ NO3- NO3- NO3- Na+ Na+ Na+ NO3- NO3- Na+ NO3- Na+ Na+

NO3- Na+ NO3- NO3- Na+ Na+ Na+ NO3- NO3- Na+ Na+ Na+ NO3- NO3- Na+ AgCl(s)

NO3- Na+ Na+ NO3- Na+ NO3- NO3- NO3- Na+ Na+ Na+ NO3- NO3- Na+ NO3- AgCl(s)

NO3- Na+ NO3- NO3- Na+ Na+ Na+ NO3- NO3- Na+ Na+ Na+ NO3- NO3- Na+ AgCl(s)

Combustion (burning) CxHy+ O2 CO2 + H2O C3H8 + O2 CO2 + H2O C2H2+ O2 Produces light and heat CxHy+ O2 CO2 + H2O Balance C 1st, then H, then O (because it splits up) 4 1 C3H8 + O2 5 CO2 + H2O 3 1 2 2.5 5 2 4 2 1 C2H2+ O2 CO2 + H2O

Classification of Equations SYNTHESIS AB A B Ca S CaS DECOMPOSITION AB A B 2HgO 2Hg O2

Classification of Equations SINGLE REPLACEMENT AB C A BC 2KCl Br2 Cl2 2KBr DOUBLE REPLACEMENT AB CD AD CB CaSO4 BaCl2 CaCl2 BaSO4

Putting it all together 1. Write the ions and element symbols. 2. Rewrite the correct formulas. 3. Balance the equation. 4. Identify the type of reaction. BEFORE this they balance equation sheet (see star) then go back and ID type of equation Iron (II) sulfide + Hydrochloric acid Iron (II) chloride + Hydrogen sulfide

1. Write the ions and element symbols Iron (II) sulfide + Hydrochloric acid Iron (II) chloride + Hydrogen sulfide Fe+2S-2 + HCl Fe+2Cl-1 + H+1S-2

2. Rewrite the correct formula. Fe+2S-2 + HCl Fe+2Cl-1 + H+1S-2 FeS + HCl FeCl2 + H2S

4. Identify the type of reaction. 3. Balance the equation. 1 FeS + HCl FeCl2 + H2S 2 1 1 4. Identify the type of reaction. Insist on them writing oxidation states BEFORE formula. Double Replacement!

Try this one. Ca0 + HCl Ca+2Cl-1 + H20 1 + HCl Ca CaCl2 + H2 2 1 1 1. Write the ions and element symbols. 2. Rewrite the correct formulas. 3. Balance the equation. 4. Identify the type of reaction. Calcium + Hydrochloric acid Calcium chloride+ Hydrogen Ca0 + HCl Ca+2Cl-1 + H20 1 + HCl Ca CaCl2 + H2 2 1 1 Single Replacement!

Try this one. Zn+2 (OH)-1 Zn+2O-2 + H2O Zn(OH)2 ZnO + H2O 1 1 1 1. Write the ions and element symbols. 2. Rewrite the correct formulas. 3. Balance the equation. 4. Identify the type of reaction. Zinc hydroxide Zinc oxide+ water Zn+2 (OH)-1 Zn+2O-2 + H2O Zn(OH)2 ZnO + H2O 1 1 1 Maybe stop here and go on own with worksheet (depend on how they handle it). Decomposition!

Try this one. N20 + O20 N+2O-2 1 N2 + O2 NO 1 2 Synthesis! Nitrogen 1. Write the ions and element symbols. 2. Rewrite the correct formulas. 3. Balance the equation. 4. Identify the type of reaction. Nitrogen Nitrogen oxide + Oxygen N20 + O20 N+2O-2 1 N2 + O2 NO 1 2 Synthesis!

Activity Series of the Elements: Table L Li Rb K Ba Sr Ca Na Mg Al Mn Zn Cr Fe Cd Co Ni Sn Pb H2 Sb Bi Cu Hg Ag Pt Au Replaces H from water Nonmetals F2 Cl2 Br2 I2 Replaces H from acids Most Active Most Active Least Active Least Active Metals replace metals or H Nonmetals replace nonmetals *REPLACE FROM OWN COLUMN

Making Predictions: Single Replacement Rxn 1. Write symbol and ions (for compounds) and predict products. 2. Rewrite correct formulas. 3. Use activity series to tell if rxn occurs and why. 4. Balance equation. Pepsi commercial Aluminum + Nickel (II) chloride ?

1. Write symbols & ions and predict products. Aluminum + Nickel (II) chloride ? Al0 + Ni+2Cl-1 Al+3Cl-1 + Ni0 2. Rewrite correct formulas. Al + NiCl2 AlCl3 + Ni

3. Use the activity series to tell if the rxn occurs and why. Yes, Al is more active than Ni. 2 Al + NiCl2 3 2 AlCl3 + Ni 3 4. Balance equation.

Now try this one. Ca0 + Co+3(NO3)-1 Ca+2(NO3)-1 + Co0 3 3 2 Ca(NO3)2 1. Write symbol and ions (for compounds) and predict products. 2. Rewrite correct formulas. 3. Use activity series to tell if rxn occurs and why. 4. Balance equation. Calcium + Cobalt (III) nitrate ? Ca0 + Co+3(NO3)-1 Ca+2(NO3)-1 + Co0 3 3 2 Ca(NO3)2 Ca 2 + Co + Co(NO3)3 Yes, Ca is more active than Co.

Now try this one. Br20 + Rb+1I-1 Rb+1Br-1 + I20 1 2 RbBr + I2 1 Br2 1. Write symbol and ions (for compounds) and predict products. 2. Rewrite correct formulas. 3. Use activity series to tell if rxn occurs and why. 4. Balance equation. Bromine + Rubidium Iodide ? Br20 + Rb+1I-1 Rb+1Br-1 + I20 1 2 RbBr + I2 1 Br2 + RbI 2 Yes, Br is more active than I.

Making Predictions: Double Replacement Rxn Double Replacements will only complete when one or more of these events occur: 1. Water forms (H2O) 2. A gas forms (g) 3. A precipitate (s) forms Do “Chapter 9 Double Replacement Reactions” first two together, rest on own.

Let’s try a couple Does the reaction occur? Does the reaction occur? Ba(OH)2 (aq) + H2SO4(aq) BaSO4(aq) + H2O(l) Does the reaction occur? YES; water is formed. What are the spectator ions? (The ions not involved in forming water, gas, or precipitate) Ba+2 & SO4-2 Ca3(PO4)2(aq) + NaNO3(aq) Na3(PO4)2(aq) + CaNO3(aq) Does the reaction occur? No; no water, gas or precipitate is formed.

Potassium chromate + copper(II) hydroxide 1. Write symbols & ions and predict products. Rewrite correct formulas and look up states of products on Table C. K+1 (CrO4)-2 + Cu+2(OH)-1 Cu+2(CrO4)-2 + K+1(OH)-1 K2 (CrO4) + Cu(OH)2 Cu(CrO4) (s) + K(OH) (aq) insoluble on Table C soluble on Table C

Does a precipitate (s) form? 1 2 Potassium chromate + copper(II) hydroxide 3. Balance equation. 4. Does reaction occur? Does water form? Does a gas (g) form? Does a precipitate (s) form? 1 2 K2CrO4 + Cu(OH)2 CuCrO4 (s) + KOH (aq) NO Do “Double Replacement Reactions” predicting Then single and double replacement reactions predicting NO YES! THE RXN OCCURS!

Writing equations from a sentence Write the equation for the production of oxygen gas and potassium chloride from the breakdown of potassium chlorate. 1. Potassium chlorate breaks down to form potassium chloride & oxygen K+1Cl-1 + O2 (g) K+1(ClO3)-1 2. Rewrite the correct formulas. KCl + O2 (g) K(ClO3) 3. Balance the equation by changing the coefficients. KCl + O2 (g) K(ClO3) 2 3

Barium hydroxide reacts with carbon dioxide to form barium carbonate and water. Barium hydroxide reacts with carbon dioxide to form barium carbonate & water Ba+2(OH)-1 + CO2 (g) Ba+2(CO3)-2 + H2O(l) Ba(OH)2 + CO2 (g) BaCO3 + H2O(l) Ba(OH)2 + CO2 (g) BaCO3 + H2O(l) 1

CaC2 + H2O(l) + C2H2(g) Ca+2(OH)-1 CaC2 + H2O (l) Ca(OH)2 + C2H2(g) 1 Calcium carbide, CaC2, reacts with water to produce calcium hydroxide & ethyne gas, C2H2. Calcium carbide reacts with water to produce calcium hydroxide & ethyne gas CaC2 + H2O(l) + C2H2(g) Ca+2(OH)-1 CaC2 + H2O (l) Ca(OH)2 + C2H2(g) CaC2 + H2O (l) Ca(OH)2 + C2H2(g) 1 2

Type of Reaction Definition Equation Synthesis Decomposition Single Replacement Double Replacement Combustion A hydrocarbon combines with oxygen to yield CO2 and water. CxHy + O2  CO2 + H2O Two or more elements or compounds combine to make a more complex substance A + B → AB Compounds break down into simpler substances AB → A + B Occurs when one element replaces another one in a compound AB + C → AC + B Occurs when different atoms in two different compounds trade places AB + CD → AC + BD

Classification of Equations SYNTHESIS AB A B Ca S CaS DECOMPOSITION AB A B 2HgO 2Hg O2

Classification of Equations SINGLE DISPLACEMENT AB A BC C 2KCl Br2 Cl2 2KBr DOUBLE DISPLACEMENT AB CD AD BC CaSO4 BaCl2 CaCl2 BaSO4

Practice 1 CH4 + O2 CO2 + H2O 1 2 2 1 C 1 C 4 H 2 H 2 O 3 O 4 O 4 O *Hint: Don’t make a move until you find the uneven side. 2 O 3 O 4 O 4 O 1 C 1 C 4 H 4 H 1 C, 4 H, 4 O 1 C, 4 H, 4 O

Practice 2 1 Na + H2O NaOH + H2 2 1 2 1 Na 1 Na 2 H 3 H 4 H 4 H 1 Na

Practice 6 C, 16 H, 20 O 6 C, 16 H, 20 O 6 8 2 C3H8 + O2 CO2 + H2O 1 1 10 1 C 3 C 6 C 6 C 2 H 16 H 16 H 16 H 2 O 20 O Do together 20 O 20 O 6 C, 16 H, 20 O 6 C, 16 H, 20 O

Practice 1 2 Ba(OH)2 + HCl BaCl2 + H2O 1 1 2 1 Ba 1 Ba 2 O 1 O 2 O 2 O 1 Ba, 4 H, 2O, 2Cl 1 Ba, 4 H, 2O, 2Cl

Practice 3 2 1 Na3PO4 + Al2(SO4)3 Na2SO4 + AlPO4 2 1 3 Na 2 Na 6 Na 6 Ba, 2P, 20 O, 2 Al, 3 S 6 Ba, 2P, 20 O, 2 Al, 3 S

Practice 2 Ca(NO3)2 + KCl KNO3 + CaCl2 1 1 2 2 3 1 3 Al(OH)3 + CaSO4 Al2(SO4)3 + Ca(OH)2 2 Al, 12 O, 3 H, 3 Ca, 1 S 2 Al, 12 O, 3 H, 3 Ca, 1 S

Activity Series of the Elements: Table L Metals Li Rb K Ba Sr Ca Na Mg Al Mn Zn Cr Fe Cd Co Ni Sn Pb H2 Sb Bi Cu Hg Ag Pt Au Nonmetals F2 Cl2 Br2 I2