Chemical reactions

What are the rules for counting atoms? Essential question What are the rules for counting atoms?

What is a subscript? SUBSCRIPTS indicate the number of atoms that an element has. They are found BEHIND that element.

There are TWO atoms of hydrogen and only ONE atom of sulfur. For example… H2S Subscript There are TWO atoms of hydrogen and only ONE atom of sulfur.

Note If there is no subscript behind an element, there is only ONE atom of that element!

What are Coefficients? COEFFICIENTS multiply the entire compound. They are found at the front of the compound

For example 2 HF Coefficient Atoms of hydrogen= 2 Atoms of fluorine= 2

What if you have subscripts and coefficients in a compound? You MULTIPLY the coefficients and subscripts.

For example 2 H2S Coefficient Atoms of Hydrogen= 4 Atoms of Sulfur= 2

How do you count atoms in Parentheses? If elements are inside of PARENTHESES, the SUBSCRIPT behind the parentheses applies ONLY to the elements inside.

For example Ba(OH)2 Atoms of barium: 1 Atoms of oxygen: 2 Atoms of hydrogen: 2

Let’s Practice together! 1) MgCl2 Atoms of Mg: Atoms of Cl: 1 2 2) 2Na(OH) Atoms of Na: Atoms of O: Atoms of H: 2 2 2

On your own K2(SO4) Atoms of K: Atoms of S: Atoms of O: 2 1 4

With a partner Practice! 3CH3OH Atoms of C: Atoms of H: Atoms of O: 3 10 1

Exit Ticket??? 2Ca3(PO4)2 Atoms of Ca: Atoms of P: Atoms of O: 6 4 16

What is a Chemical reaction? A process whereby one or more substances are changed into one or more products

These are the original substances before the reaction occurs What are reactants? These are the original substances before the reaction occurs

These are the resulting substances after the reaction has occurred What are products? These are the resulting substances after the reaction has occurred

What is the Law of Conservation of Mass? The total mass of the reactants must be equal to the mass of the products for any chemical reaction **This is the reason why we count atoms

Why do we count atoms? Mass is neither created or destroyed The law of conservation of mass must be satisfied for all chemical equations and reactions Mass is neither created or destroyed The same number of atoms of each element must appear on each side of a chemical equation

How are chemical reactions represented? Chemical reactions are represented with chemical equations

What do symbols in Chemical Equations mean?

How do we know a chemical reaction occurred? Heat and light are produced Gas produced Color change Precipitate (s) formed

How do you balance a chemical equation? Step 1: Work in pencil!

How do you balance a chemical equation? Step 2: List the elements present on the reactant side and the product side

How do you balance a chemical equation? Step 3: Count the number of atoms for each element on each side

How do you balance a chemical equation? Step 4: Add a COEFFICIENT ONLY to the compounds that will make the number of atoms equal on both sides

Important!!! The Coefficient must ALWAYS go to the front of the compound Subscripts cannot be changed

Let’s try together ___N2 + ___H2  ___NH2 Balance the following ___N2 + ___H2  ___NH2 ___Al + ___FeN2  ___AlN + ___Fe ___AgNO3 + ___Cu  ___Cu(NO3)2 + ___Ag

Snowman Challenge

What are the five types of Chemical reactions? The five types are: Synthesis Decomposition Single Replacement Double Replacement Combustion

What is a Synthesis reaction? Two or more substances come together to form a new compound General equation: A + X  AX Ex. S + O2  SO2

Celebrity Synthesis reaction (Marriage) Beyonce +Jay-Z ✚ 

What is a Decomposition reaction? A single compound is broken down into simpler substances General equation: AX  A + X Ex. 2H2O2  2H2O + O2

Celebrity Decomposition (Divorce) Mariah Carey + Nick Cannon  ✚

What is a Single Replacement reaction? One element replaces another element in a compound General equation: A + BX  AX + B Ex. Mg + 2HCl  MgCl2 + H2

Celebrity Single Replacement reactions Brad and Jennifer w/ Angelina ✚ 

What is a Double Replacement reaction? Two compounds exchange elements to form two new compounds General equation AX + BY  AY + BX Ex. FeS + 2HCl  FeCl2 + H2S

Celebrity Double Replacement?

What is a Combustion reaction? A hydrocarbon combines with O2 to produce CO2 and H2O General equation: CH + O2  CO2 + H2O Ex. C3H8 + 5O2  3CO2 + 4H2O

Celebrity Combustion Chris Brown and Rihanna

How do we know what state of matter a compound is? Look at your Solubility Chart!

What does soluble mean? Can be dissolved

What does Aqueous(aq)mean? Dissolved in water

What does insoluble mean? Cannot be dissolved

What does precipitate mean? A solid has been formed

If the products produced are (aq) + (aq), what is formed? A solution No chemical reaction has occurred

If one of the products is a precipitate (s) A chemical reaction will happen

What must be produced for a chemical reaction to occur? A precipitate (a solid)

Solubility practice Identify the following as Solid (s) or Aqueous(aq) NaCl Cu(NO3)2 CaCO3 Fe2S3