Chemical Reactions Introduction Unit 5 Chemical Reactions Introduction

Chemical Reactions A chemical reaction occurs when a substance (or substances) change(s) into a new substance(s) with a new identity. Chemical bonds are broken, and atoms rearrange and form new bonds. A chemical equation is used to express the chemical reaction.

A + B → C + D Chemical Reactions Reactants The matter that is present before the reaction takes place. Reactants are always to the left of the arrow. A + B → C + D

A + B → C + D Chemical Reactions Products The matter that is present after the reaction takes place Products are always to the right of the arrow A + B → C + D

A + B → C + D Chemical Reactions Yield Sign The arrow, →, is read as the word, yields. What the yield sign is saying is that the reactant(s), when combined or dissolved, form the product(s). A + B → C + D

Chemical Reactions Zn + 2AgNO3 → Zn(NO3)2 + 2Ag The subscripts show how many of each element. Zn + 2AgNO3 → Zn(NO3)2 + 2Ag Ex. There is 1 Zinc There are 2 Nitrates Coefficients - How many of the entire molecule. Acts as a multiplier for the entire compound. 2AgNO3 There are 2 - Silver Nitrates

Chemical Reactions Symbols often seen in chemical equations…… (s) – Solid:A solid precipitate can form as a result of a chemical reaction (l) - Liquid (g) - Gas Often seen as bubbles (aq) - Aqueous Solution Compound is dissolved in water

5 Types of Chemical Reactions Synthesis Decomposition Single Replacement Double Replacement Combustion Synthesis - 2 or more reactants combine to form a single product. A + B → AB 4Fe + 3O2 → 2Fe2O3

Types of Chemical Reactions Decomposition - One reactant yields two or more products. AB → A + B H2SO3 → H2O + SO2 Single Replacement - One element takes the place of another element. A + BC → AB + C Cl2 + 2NaBr → 2NaCl + Br2

Types of Chemical Reactions Double Replacement - The positive ions of two ionic compounds switch places. At least one of the products will be a precipitate, water, or gas. AB + CD → AD + CB Pb(NO3)2 (aq) + 2 KI (aq) → PbI2 (s) + 2 KNO3 (aq)

Types of Chemical Reactions Combustion - Burning an organic substance. The products are always CO2 and H20. ****Often a hydrocarbon combines with O2. Combustion is what makes an engine run. CH4 + 2O2 → CO2 + 2H20

HUSKY HELP 10-27-16 IF you want to retake the test from Tuesday… get out your completed Remediation sheet off of Weebly  HMWK: Work on HP Part 4—Research Paper .. Individually Due Nov. 15th

Thursday….10-27-16 Get a Lab worksheet off the front table… read over it and get ready for a short lab By the end of this unit… you will write a balanced chemical equation for what is occurring in the lab HMWK: Work on HP Part 4—Research Paper .. Individually Due Nov. 15th

Types of Chemical Reactions

Get out your notes from yesterday… Get a sheet of construction paper… fold it into four squares. You will create one cartoon for each of the following chemical reactions in each square. Make sure you label each one correctly. 1. Synthesis 2. Decomposition 3. Single replacement 4. Double replacement Do not copy my example. Then…. You will have one person report out and show them to the class and then we will Hang them in the hallway

Warm-up…. 10-28-16 What type of Reaction is shown? NaBr + Ca(OH)2 → CaBr2 + NaOH NH3+ H2SO4 → (NH4)2SO4 C5H9O + O2 → CO2 + H2O Pb + H3PO4 → H2 + Pb3(PO4)2 CaCO3 → CaO + CO2 HBr + Al(OH)3 → H­2O + AlBr3

What type of Reaction is shown? NaBr + Ca(OH)2 → CaBr2 + NaOH NH3+ H2SO4 → (NH4)2SO4 C5H9O + O2 → CO2 + H2O Pb + H3PO4 → H2 + Pb3(PO4)2 CaCO3 → CaO + CO2 HBr + Al(OH)3 → H­2O + AlBr3 Double Replacement Synthesis Combustion Single Replacement Decomposition

Predicting Products Predict the products: If there are two elements as reactants, then the reaction is SYNTHESIS. If there is one reactant, then the reaction is DECOMPOSITION. Predict the products: Mg + O2 → Ca + Cl2 → Li2O → ZnCl2 → K + S → MgO CaCl2 Li + O2 Zn + Cl2 K2S

Predicting Products For Single Replacement reactions: * Use ACTIVITY SERIES (in your reference tables)* The element that is by itself MUST be hig her on the chart than the element in the compound for the reaction to occur Metal replace Metals Nonmetals replace Nonmetals

Will the reaction occur? Fe (s) + Pb(NO3)2 (aq) → Ni (s) + MgCl2 (aq) → Cl2 (aq) + NaI (aq) → Ca (s) + CuBr2 (aq) → K (s) + Al(NO3)3 (aq) → I2 (s) + MnBr2 (aq) → Mg (s) + AgNO3 (aq) → Cl2 (s) + SrF2 (aq) → YES NO Take the reactions that WILL occur and predict the products.