Chapter 11, Chemical Reactions Day 1 is slides 1-30

Chemical Equation:

chemical equation is a representation of a chemical reaction reactants (on left) and products (on right) are expressed as chemical formulas. Reactants = IN Products = OUT

law of conservation of mass mass is neither created nor destroyed in a chemical reaction

law of conservation of mass says whatever is put into the reaction must come out as products. i.e., if you put 3 oxygen in, then you must get 3 oxygen out. Same number of each atom on both sides.

Conservation of mass: Put Same number of each atom on both sides. (Show brainpop on conservation of mass.)

Review 1 st slide This equation violates the Law of Conservation of Mass. Why? This is unbalanced. Will balance in later slides.

Coefficients 2Na 2 S = 4Na and 2S This means 2 units of sodium sulfide How many atoms in each of the following 4MgCl 2 = 2Na 2 CO 3 = 3Fe 2 (SO 4 ) 3 =

This means 2 units of sodium sulfide 2Na 2 S = 4Na and 2S How many atoms in each of the following 4MgCl 2 = 4Mg, 8Cl 2Na 2 CO 3 = 4Na, 2C, 6-O 3Fe 2 (SO 4 ) 3 = 6Fe, 9S, 36-O Got it? Do in your notes now. 4(NH 4 ) 2 S

^ unbalanced equation^ there are not the same number of each type of atom on both sides of the equation

TO BALANCE: 1.)Only add coefficients (must be lowest whole numbers) 2.) Never change subscripts CO is not the same as CO 2 !!!!! Now there are the same number of atoms on both sides of the equation

Diatomic Elements: There are 7 diatomic elements, don’t forget that these only exist as diatomic gases. H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 Cl I F H. Br O N Says there are 7.

Try these. Teacher Note. Do all through slide 17 before reviewing ans on 18 Na + F 2  NaF

H 2 + O 2  H 2 O

Al + O 2 

Al + O 2  Al 2 O 3

Na + F 2  NaF H 2 + O 2  H 2 O Al + O 2  Fe(OH) 2 + HCl  FeCl 2 + H 2 O

Answers 2Na + F 2  2NaF 2H 2 + O 2  2H 2 O 4Al + 3O 2  2Al 2 O 3 Fe(OH) 2 + 2HCl  FeCl 2 + 2H 2 O

Catalyst: A substance not used up in a reaction that speeds up the reaction. Table above is on Pg 348 of text

What is a catalyst? A substance that speeds up a reaction, without being changed or used up by the reaction. Enzymes are biological or protein catalysts in your body.

Copy and write a balanced equation Solid copper reacts with oxygen gas to form solid copper I oxide.

Copy and write a balanced equation Solid copper reacts with oxygen gas to form solid copper I oxide. 4Cu (s) +O 2(g)  2Cu 2 O (s)

Balance it. What whole number coefficient will go in front of CaO? Ca + O 2  CaO A)1B) 2C) 3D)4

Quiz #1 1. Mg + S  MgS 2. Na + O 2  Na 2 O 3. NaOH  Na 2 O + H 2 +O 2 4. LiCl  Li + Cl 2 5. C 18 H 38 + O 2  CO 2 + H 2 O

Quiz #1 Answers 1. Mg + S  MgS

Quiz #1 Answers 2. 4Na + O 2  2Na 2 O

Quiz #1 Answers 3. 4NaOH  2Na 2 O + 2H 2 +O 2

Quiz #1 Answers 4. 2LiCl  2Li + Cl 2

Quiz #1 Answers 5. 2C 18 H O 2  36CO H 2 O

Quiz #1 Answers 1. Mg + S  MgS 2. 4Na + O 2  2Na 2 O 3. 4NaOH  2Na 2 O + 2H 2 +O LiCl  2Li + Cl C 18 H O 2  36CO H 2 O

Day 2. Next Section: Predicting Possible Products

The goal of this unit is going to be predicting possible products in a chemical reaction and then balancing the final equation. (Charges? How can they help?) K + O 2  ?

Charges? How can they help? Review Group1A = +1 2A = +2 3A = +3 5A = -3 6A = -2 7A = -1

Pg 348

There are 7 diatomic elements, don’t forget that these only exist as diatomic gases. H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 Cl I F H. Br O N Says there are 7 diatomic elements.

Types of reactions. Cl I F H. Br O N Says there are 5 types of reactions.

Types of Reactions There are probably millions of reactions. We can’t remember them all, but luckily they will fall into several categories. We will learn: a) the 5 major types. We will be able to: b) predict the products. For some, we will be able to: c) predict whether or not they will happen at all. How? We recognize them by their reactants

Define: A,B,C are variables for elements A,B,C… = ionic compound, molecular compound, atom, acid, base, metal, non- metal, or polyatomic ion, etc.

combination reaction: things combine into 1 thing. Note: rxn is reaction. Two or more substances react to form a single substance. They combine together. A + B  AB 2Na (s) + Cl 2(g)  2NaCl (s)

combination reaction (rxn) - two or more substances react to form a single substance Δ 2H 2(g) + O 2(g)  2H 2 O (/)

Try it Li + S 

Try it Li + S  Li 2 S Li has a +1 charge S has a -2 charge Remember the crisscross rule. There must be a 2:1 ratio for the charges to cancel.

Now Balance 2Li + S  Li 2 S

Mg + O 2  Steps: 1. Find product 2. Balance

Mg + O 2  MgO Mg has a +2 charge and O has a -2 charge… this is the only product that forms. The net charge is zero. Any time that a metal and a nonmetal react you can predict their products based on each of the elements common ionic charges.

Balance it! 2Mg + O 2  2MgO

K+S 

decomposition rxn = Compound breaks into parts. a compound breaks down into two or more simpler substances AB  A + B ABC  A + B + C 2H 2 O  2H 2 + O 2

#2 - Decomposition Reactions If the compound has more than two elements you must be given one of the products –The other product will be from the missing pieces NiCO 3 CO 2 + ___ H 2 CO 3 (aq)  CO 2 + ___ heat

#2 - Decomposition Reactions We can predict the products if it is a binary compound (which means it is made up of only two elements) –It breaks apart into the elements: H 2 O HgO

#2 - Decomposition Reactions We can predict the products if it is a binary compound (which means it is made up of only two elements) –It breaks apart into the elements: 2H 2 O 2H 2 + O 2 2 HgO 2Hg + O 2

Try it Δ Na 2 O  Are either of these diatomic elements? Can you predict if the products are gases or will be solids based on their position on the periodic table?

What type of reaction is this? H 2 + F 2  2HF A) Combination B) Decomposition C) Double-Replacement D) Combustion

To solve: 1. Predict products. 2. Write skeleton eqn. 3. Balance the eqn.

Single-replacement rxn = One element replaces another. one element takes the place of another element in a compound.

Remember from before: H 2 0 is really HOH or H + OH - So only the first H + will swap. The second H will NOT swap.

Ba + Na 2 SO 4  Will the metals replace each other? The more reactive metal will combine with the anion. Remember discussing reactivities in the periodic table. Lower left is most reactive. Activity Table.: Is there an easier way? Yes, look at page 361, table The metal highest up in the table will be the one that ends up attached to the anion.

Ba + Na 2 SO 4  Assume the metals will replace each other. Do Ba and Na have the same common ionic charge? Is Na diatomic? What is the charge of sulfate?

Li + H 2 O  A group 1 metal can replace ONE H from an acid and/or water. If one H is removed from water than OH- remain; hydroxide.

Try it Na + Cs 2 O  Assume that the metal will replace the other metal in the compound. Is the common ionic charge of Na and Cs similar? Is Cs a diatomic element?

Double-replacement rxn = two compounds swap an element two different compounds exchange positive ions and form two new compounds.

Try it AgNO 3 + NaCl  Assume the metals will switch places. How do you find the charge of Ag? Are the charges on the metals similar?

NaOH+ HCl  Assume Na and H will switch places. Are their charges similar? What is HOH?

H 2 SO 4 + Al(OH) 3  Assume that the Al and H switch places. Are the charges on Al and H the same? The net charge of the products must be equal to zero.

Combustion reaction = reacts with oxygen. a substance reacts with oxygen often producing heat and light C X H X + O 2  CO 2 + H 2 O

Combustion reaction = reacts with oxygen. Often we look at Hydrocarbon Combustion. What products does Hydrocarbon Combustion always produce? C X H X + O 2  CO 2 + H 2 O

Li + O 2  What are the common ionic charges of these ions? The net ionic charge of the product must be equal to zero.

C 7 H 16 + O 2  What are always the two products of the combustions of a CH compound?

Try it Watch the demonstration and try to write a balanced equation for what you are seeing.

What type of rxn is this? NaOH +HCl  NaCl + H 2 O A) Combination B) Decomposition C) Double-Replacement D) Combustion

Predict and balance HI 

Predict and balance 2HI  I 2 + H 2

Predict and balance Na + O 2 

Predict and balance 4Na + O 2  2Na 2 O combination

Predict and balance Li + Al 2 O 3 

Predict and balance Li + Al 2 O 3  Li 2 O+ Al Single replacement

Predict and balance HNO 3 + NaOH 

Predict and balance HNO 3 + NaOH  H 2 O + NaNO 3

Combination reaction: things combine into 1 thing. A + B  AB 2  1 Decomposition rxn = Compound breaks into parts. AB  A + B 1  2 Single-replacement rxn = One element replaces another. A + BC  B + AC 2  2 1 Elem Double-replacement rxn = two compounds swap an element AB + CD  AD + CB 2  2 Both Comp Combustion reaction = reacts with oxygen. + O 2 

Aqueous: (aq) dissolved in water Double replacement reaction involving 2 solutions Precipitate: a solid that forms in a liquid and stops the reaction from being reversible. NaCl(aq) + AgNO 3 (aq)  NaNO 3 (aq) + AgCl(s)

NaCl (s) + H 2 O (l) = Na + (aq) + Cl - (aq) Ionic compounds dissociate into ions in solution

Na + (aq) + Cl - (aq) + Ag + (aq) + NO 3 - (aq)  Na + (aq) + NO 3 - (aq) + AgCl (s) complete ionic equation – shows free ions in solution

Ag + (aq) + Cl - (aq)  AgCl (s) Net ionic equation = shows only the ions that react to form a solid (precipitate), the rest of the ions remain in solution and are called spectator ions

Try it. Write the net ionic equation. (Predict products) BaCl 2(aq) + Na 2 SO 4(aq) 

Try it. Write the net ionic equation. BaCl 2(aq) + Na 2 SO 4(aq)  BaSO 4(s) + NaCl (aq)

Try it. Write the net ionic equation. Ba 2+ (aq) + SO 4 2- (aq)  BaSO 4(s)

Try it? p. 344 NaCl (aq) + CaCl 2(aq) 

Pb(NO 3 ) 2 (aq) + NaCl (aq) 

Lab p345, Questions 1-5