Presentation on theme: "1. Recognize Evidence of a chemical change. 2. Represent chemical reactions with equations. 3. Change word equations into formula equations. 4. Given."— Presentation transcript:
1. Recognize Evidence of a chemical change. 2. Represent chemical reactions with equations. 3. Change word equations into formula equations. 4. Given a description of a reaction, write a word and formula equation. 5. Balance chemical equations. 6. Translate a formula equation into a sentence. 7. Define and give a description of the major types of chemical reactions. 8. Classify reactions as one of five major types. 9. Predict the products of simple reactions when given the reactants. 10. Understand, explain, and apply the activity series of the elements.
1. Memorize the diatomic elements 2. Memorize the symbols used in chemical equations. 3. Use the Activity Series for single replacement reactions 4. Use the Solubility Chart for Double Replacement Reactions 5. Know common gases 6. Memorize substances that decompose Carbonic acid, H 2 CO 3 H 2 CO 3 (aq) H 2 O+ CO 2(g) Sulfurous acid, H 2 SO 3 H 2 SO 3 (aq) H 2 O + SO 2(g) Ammonium hydroxide, NH 4 OH NH 4 OH (aq) H 2 O + NH 3(g)
The process by which one or more substances are rearranged to form different substances is called a chemical reaction.chemical reaction Also called a chemical change Activity 1: Name Some Common Chemical Reactions
o the reactants which enter into a reaction. o the products which are formed by the reaction. o the relative amounts of each substance used and each substance produced. o Reactants Products
Every chemical compound has a formula which cannot be altered. A chemical reaction must account for every atom that is used. This is an application of the Law of Conservation of Matter which states that in a chemical reaction atoms are neither created nor destroyed.
Activity #2 Indicators of a chemical reaction Procedure 1. Add 10.0 mL od distilled water to a small beaker. 2. Add 1 drop of.1 M NaOH to the water. 3. Add 15 drops of universal indicator to the water. Stir. 4. Record the color of the water. 5. Record the temperature of the water. 6. Drop an alka seltzer tablet into the water. 7. Observe the reaction. Record all observations including any temperature change. Analysis Questions Describe any color changes or temperature changes. Was a gas produced? How do you know? Did chemical change occur? Explain how you know. What is the purpose of the universal indicator? Make a list of five indicators of a chemical reaction.
Production of a Gas Temperature Change Color Change Production of a Solid (precipitate) Production of Water or other unionized substance
We use chemical equations to represent reactions Ways to show equations Sentence Descriptions Word Equations Skeleton Equations Balanced Chemical Equation
Every item is a word. Copper reacts with chlorine to form copper (II) chloride Iron (III) chloride is produced from iron metal reacting with chlorine gas
Words and symbols are used. Copper + chlorine copper (II) chloride iron (s) + chlorine (g) iron(III) chloride (s)
Uses chemical formulas instead of words Fe (s) + Cl 2 (g) FeCl 3 (s)
2Fe (s) + 3Cl 2 (g) 2FeCl 3 (s)
The diatomic elements are always written H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 The sign, →, means "yields" and shows the direction of the action. A small delta, ( ), above the arrow shows that heat has been added. A double arrow, ↔, shows that the reaction is reversible and can go in both directions.
In order to obey the Law of Conservation of Mass equations must be Balanced: Coefficients: number written in front of a chemical formula to indicate the smallest number of particles involved in the reaction.
Write skeleton equation. Change the coefficients to make the number of atoms of each element equal on both sides of the equation. NEVER CHANGE A SUBSCRIPT!!! Write the coefficients in the smallest ratio possible. Check your work.
Start with “Big Formulas” C 2 H 6 O 2 Save single elements for last O 2 or Cu Balance hydrogens second to last Balance oxygens last Check for lowest ratio Do not change your subscripts Balance the polyatomic ions as one unit (if it didn’t break apart) Perform a final check
If your equation doesn’t balance, check your formulas!!
Five Types of Chemical Reactions Synthesis Reaction Decomposition Reaction Single Replacement Reaction Double replacement Reaction Combustion Reaction: oxygen combines with a substance and produces heat and light
Synthesis Reaction: one product is formed from more than one simpler substances A + B AB Activity: Reaction of Iron with Oxygen Gas
Decomposition Reaction: One substance is broken down into one or more simpler substances: usually by the addition of energy AB A + B Activity: Elephant Toothpaste
Single Replacement Reaction: atoms of one element replace another element in a compound A + BC B + AC Activity: Reaction of iron with copper (II) nitrate
Involves the exchange of ions between two compounds AB + CD AD + CB Activity: Copper (II) chloride reacts with sodium hydroxide
Oxygen combines with a substance and produces heat and light Most likely: Hydrocarbon (C x H y ) Combustion C x H y + O 2 H 2 O + CO 2 X + O 2 X 2 O 3 Demo: Methane Snake
Ca + O 2 CaO Br + LiI LiBr + I Al + Fe(NO 3 ) 2 Al(NO 3 ) 3 + Fe MgO + HCl MgCl 2 + H 2 O C 4 H 10 + O 2 CO 2 + H 2 O NH 4 NO 2 NH 3 + H 2 O (NH 4 ) 3 PO 4 + Sr(OH) 2 Sr 3 (PO 4 ) 2 + NH 4 OH H 2 SO 4 + NaOH Na 2 SO 4 + H 2 O Zn + AgNO 3 Zn(NO 3 ) 2 + Ag CuNO 3 + KCl KNO 3 + CuCl
Given the reactants predict what is formed Write formulas for reactants Identify the type of reaction Rearrange the atoms to write formulas for products.
Atoms of one element replace another element in a compound A + BC B + AC There are 3 Ways that a Single Replacement Reaction can occur.
when zinc combines with iron (II) chloride the zinc replaces iron in the compound Z n + FeCl 2 Fe + ZnCl 2
Br 2 + LiI LiBr + I 2
Use the activity series of the elements If the free element is more active than the element in the compound the reaction will happen If the free element is below the element in the compound the reaction will not happen
Bigger, stronger, orange shirted guy replaces white shirt guy in the dancing couple Now we have new couple and new single guy
ps/chm/100/dgodambe/thedisk/se ries/3perform.htm Some Examples to Observe before lab
two ionic compounds are mixed together in water In water the ionic compounds split into anions and cations. The cations have an opportunity to swap anions A reaction occurs, if by swapping anions, a product is formed that cannot split apart into anions and cations AB + CD AD + CB
A reaction occurs when a pair of ions comes together to produce a substance that removes ions from the solution. one of the following must occur a precipitate: a solid produced during a reaction a gas Water or other unionized substance a product that decomposes online.com/objects/ViewObject.aspx?ID=gch1404 online.com/objects/ViewObject.aspx?ID=gch1404
What happens when one of the three possible products is not formed? Nothing All ions remain in solution (dissolved) NaNO 3 (aq) + KCl (aq) � � NaCl (aq) + KNO 3 (aq)
Without a driving force there is no change in the solution so we say No Reaction has taken place
S ome double replacement reactions produce a gas. We observe this as bubbles or odors given off. Example: Na 2 S ( aq ) + H 2 SO 4 ( aq ) Na 2 SO 4 ( aq ) + H 2 S(g)
Some metathesis reactions do not give the product expected. the expected product (H 2 CO 3 ) decomposes to give a gaseous product (CO 2 ) CaCO 3 ( s ) + HCl ( aq ) CaCl 2 ( aq ) + H 2 CO 3 CaCO 3 ( s ) + HCl ( aq ) CaCl 2 ( aq ) + CO 2 ( g ) + H 2 O ( l ) Products that Decompose H 2 SO 3 H 2 O + SO 2 H 2 CO 3 H 2 O + CO 2 NH 4 OH H 2 O + NH 3
These water molecules increase the number of solvent molecules and we see no observable evidence Usually accompanied by temperature change or Neutralization which can be seen with an acid base indicator Example: H 2 SO 4 + NaOH Na 2 SO 4 + H 2 O
Generally, when solutions of an acid and a base are combined, the products are a salt and water HC 2 H 3 O 2 ( aq ) + NaOH ( aq ) NaC 2 H 3 O 2 ( aq ) + H 2 O ( l ) Acid + Base Salt + Water
The molecular equation lists the reactants and products in their molecular form. AgNO 3 ( aq ) + KCl ( aq ) AgCl ( s ) + KNO 3 ( aq )
In the ionic equation all strong electrolytes (strong acids, strong bases, and soluble ionic salts) are dissociated into their ions. This more accurately reflects the species that are found in the reaction mixture. Ag + ( aq ) + NO 3 - ( aq ) + K + ( aq ) + Cl - (aq)
To form the net ionic equation, cross out anything that does not change from the left side of the equation to the right. Ag + (aq) + NO 3 - ( aq ) + K + (aq) + Cl - ( aq ) AgCl ( s ) + K + (aq) + NO 3 - ( aq )
The only things left in the equation are those things that change (i.e., react) during the course of the reaction. Ag + (aq) + Cl - ( aq ) AgCl ( s )
Those things that didn’t change (and were deleted from the net ionic equation) are called spectator ions. Ag + ( aq ) + NO 3 - ( aq ) + K + ( aq ) + Cl - ( aq ) AgCl ( s ) + K + ( aq ) + NO 3 - ( aq )
Write a balanced molecular equation. Dissociate all strong electrolytes (strong acids, strong bases, and soluble ionic salts) Cross out anything that remains unchanged from the left side to the right side of the equation. Write the net ionic equation with the species that remain.
Hydrocarbon + oxygen CO 2 + H 2 O Hydrocarbon: A compound of hydrogen and carbon The phrase "To burn" means to add oxygen unless told otherwise.
Complete Combustion: Hydrocarbon + oxygen CO 2 + H 2 O Complete combustion means the higher oxidation number is attained. Incomplete Combustion: Hydrocarbon + oxygen CO + H 2 O Incomplete combustion means the lower oxidation number is attained.
If oxygen is sufficient, the products are carbon dioxide and water vapor. If oxygen is low, carbon monoxide will be produced. automobile engine inside a closed garage or charcoal grill indoors.
Hydrocarbon (C x H y ) + O 2(g) → CO 2(g) + H 2 O (g) EX. CH 4(g) + 2O 2(g) → CO 2(g) + 2H 2 O (g) EX. 2C 4 H 10(g) + 13O 2(g) → 8CO 2(g) + 10H 2 O (g)
C 3 H 8 + O 2 --> CO 2 + H 2 O propane 3 carbons = 3 carbon dioxide molecules 8 hydrogen atoms = four H 2 O molecules. balance the oxygen
This combustion of acetylene reaction is exothermic, and enough energy is released to melt metal. Used in welding. Why So Hot??
Triple bond -multiple bonds -short bond length
Demo: Methane Snake Reaction CH 4 + 2O 2 CO 2 + 2H 2 O
A + B AB Elem/Cmpd + Elem/Cmpd Compound One Product
Metal + oxygen → metal oxide 2Mg (s) + O 2(g) → 2MgO (s) Nonmetal + oxygen → nonmetallic oxide C (s) + O 2(g) → CO 2(g) Metal oxide + water → metallic hydroxide MgO (s) + H 2 O (l) → Mg(OH) 2(s) Nonmetallic oxide + water → acid CO 2(g) + H 2 O (l) → ; H 2 CO 3(aq) Metal + nonmetal → salt 2 Na (s) + Cl 2(g) → 2NaCl (s) A few nonmetals combine with each other 2P (s) + 3Cl 2(g) → 2PCl 3(g) These two reactions must be remembered: N 2(g) + 3H 2(g) → 2NH 3(g) NH 3(g) + H 2 O (l) → NH 4 OH (aq)
AB A + B Compound Cmpd/Elem + Elem/Cmpd One Reactant
Metallic carbonates, when heated, form metallic oxides and CO 2(g) CaCO 3(s) → CaO (s) + CO 2(g) Most metallic hydroxides, when heated, decompose into metallic oxides and water Ca(OH) 2(s) → CaO (s) + H 2 O (g) Metallic chlorates, when heated, decompose into metallic chlorides and oxygen 2KClO 3(s) → 2KCl (s) + 3O 2(g) Some acids, when heated, decompose into nonmetallic oxides and water H 2 SO 4 → H 2 O (l) + SO 3(g) Some oxides, when heated, decompose 2HgO (s) → 2Hg (l) + O 2(g) Some decomposition reactions are produced by electricity 2H 2 O (l) → 2H 2(g) + O 2(g) 2NaCl (l) → 2Na (s) + Cl 2(g)
A + B AB (synthesis) AB A + B (decomposition) A + BC B + AC (single replacement) AB + CD AC + BD (double replacement) Hydrocarbon + oxygen CO 2 + H 2 O (combustion/oxidation)