Chemical Reactions Reaction Types

OUTCOME QUESTION(S): C11-3-06 NAMING AND EQUATIONS Write the formulas and/or names for any general ionic, covalent, or polyatomic compound. Write and classify balanced chemical equations from written descriptions of reactions. Classify the type of reaction and predict the products to create a complete balanced equation. Vocabulary & Concepts 

How do you make this “equation” balanced by adding stuff? Chemical equations – contain all necessary info about a reaction (like a recipe). How do you make this “equation” balanced by adding stuff? + +

In any chemical reaction matter cannot be created or destroyed. The Law of Conservation of Mass: In any chemical reaction matter cannot be created or destroyed. H2 (g) + O2 (g) H2O (g) 2 2 H H O H H O O H H H H O was This equation is unbalanced because the atoms are not conserved from one side (reactants) to the other (products)

Rules for Balancing Equations You cannot change the formula of any reactant or product. 2. You can only change the coefficients in front of the reactants and products. Coefficients of 1 are not typically written The coefficients tell you how many water molecules there are… The subscripts tell you how many hydrogen atoms are in each water… 3 H2O

2 HCl + MgBr2 MgCl2 + HBr 2 Balanced H: 1 H: 1 (2) = 2 (2) = 2 Cl: 1 Cl: 2 Mg: 1 Mg: 1 Br: 2 Br: 1 (2) = 2 (2) = 2 (2) = 2 (2) = 2 We want to get to a place where this work happens in our head with minimal notation work Balancing Tips: Find a way to track it that is meaningful to YOU. Balance metals first, then non-metals. Balance single elements last. Check and recount all the atoms. Prepare for trial and error.

2 LiI + MgO MgI2 + Li2O Balanced Try using a system (here are dots) to track balanced atoms – when all reactants have dots, it’s balanced! 2 LiI + MgO MgI2 + Li2O Balanced Balancing Tips: Find a way to track it that is meaningful to YOU. Balance metals first, then non-metals. Balance single elements last. Check and recount all the atoms. Prepare for trial and error.

2 2 Balanced K(NO3) + Mg Mg(NO3)2 + K Balancing Tips: Find a way to track it that is meaningful to YOU. Balance metals first, then non-metals. If polyatomic ion is intact on both sides – balance as a whole unit. Balance single elements last. Check and recount all the atoms. Prepare for trial and error.

Balanced 2 K2O + Cl KCl + O (s) 2 2 (g) 4 2 (g) Solid potassium oxide and chlorine gas react to produce potassium chloride and oxygen gas. +1 -2 +1 -1 + + potassium oxide chlorine Potassium chloride oxygen Balanced 2 K2O + Cl KCl + O (s) 2 2 (g) 4 2 (g) Strategies: Isolate the reactants and products (look for key words) Write the reactants, reform (re-criss cross) the products The goal is to be able to convert any written equation to an actual equation Balance and include phases/states (if given)

Many reactions are similar. Chemists have classified 5 types of reactions BIG PICTURE IDEA: If you know the reactants - you can guess the type of reaction AND predict the products Synthesis reactions Decomposition reactions Single replacement reactions Double replacement reactions Combustion reactions

You have to “re-criss cross” the product valences too Synthesis Reactions (Combination): 2 or more substances react to form a single substance. A + B  C You have to “re-criss cross” the product valences too 2 K + Cl2 KCl Fe + O2 Fe2O3 2 4 3 2

Decomposition products can be hard to predict Decomposition Reactions: A single compound splits apart, into two or more simpler compounds. C  A + B Decomposition products can be hard to predict CO2 CO + O2 Al2S3 Al + S 2 2 2 3

“Re-criss cross” the product valences… Single Replacement Reactions: One element replaces another element in a compound. More active elements replace less active elements. A + BC  AC + B “Re-criss cross” the product valences… 2 2 I2 + CuCl Cl2 + CuI Ba + K(NO3) K + Ba(NO3)2 2 2

We always write the positive ion first in a compound! Double Replacement Reactions: 2 compounds split and exchange positive ions AB + CD  AD + CB 2 2 BaF2 + LiBr BaBr2 + LiF HCl + AlBr3 HBr + AlCl3 3 3 We always write the positive ion first in a compound!

CxHy + O2  CO2 + H2O 8 7 3 5 3 4 C7H6O + O2 CO2 + H2O (Carbon) Combustion Reactions: Oxygen reacts with a carbon compound to produce water, carbon dioxide and heat. CxHy + O2  CO2 + H2O Combustion reactions ALWAYS react with oxygen to produce carbon dioxide and water C7H6O + O2 CO2 + H2O C3H8 + O2 CO2 + H2O 8 7 3 5 3 4

Synthesis A + B  C Decomposition C  A + B Single replacement A + BC  B + AC Double replacement AC + BD  AD + BC Carbon Combustion CxHy + O2  CO2 + H2O

C11-3-06 NAMING AND EQUATIONS CAN YOU / HAVE YOU? C11-3-06 NAMING AND EQUATIONS Write the formulas and/or names for any general ionic, covalent, or polyatomic compound. Write and classify balanced chemical equations from written descriptions of reactions. Classify the type of reaction and predict the products to create a complete balanced equation. Vocabulary & Concepts