Balancing Chemical Equations

ANNOUNCEMENTS! Research Outline-Rough Draft: due: Feb 5 - 6 Title Page # Forming & Naming Notes 53 Forming & Naming IP (4) 54 Book Learning 55 Naming/Writing Chemical Formulas 56 Naming/Writing IP (5) 57 Balancing Equations Notes 58 Balancing Lab 59 60 Balancing IP (3) 61 ANNOUNCEMENTS! Housekeeping Rules, Door, Attention signal Tutoring – 2:15 (NO TUESDAYS) Sign log Research Outline-Rough Draft: due: Feb 5 - 6 Class website: www.kinga2.weebly.com Your classwork is homework if not finished Work can be checked ANY day/time Double check your work! Research Topic Check

Law of Conservation of Mass Law of Conservation of Mass: States that mass is neither created nor destroyed in any ordinary chemical reaction More simply: the number of atoms for an element on the reactant side must equal the number of atoms on the product side

Counting Atoms Subscripts & (Parenthesis) An uppercase letter next to a lower case letter represents ONE element; example: Na (sodium) If there is not a number behind the element you can say you have one atom of that element; Example: CO2 you have 1 carbon atom. When a number is “small” and sits BEHIND an element, we call that a subscript. Example (N2) When there are parentheses around a compound & and a subscript outside, the subscript multiplies EVERYTHING in the ( ). Example: (PO3)4 P = 1 x 4 = 4 O = 3 x 4 = 12

Counting Atoms Subscripts & (Parenthesis) 2 minutes Counting Atoms Subscripts & (Parenthesis) My example: NaCl Na=_____ Cl=____ The next examples you are trying with a partner - 2 minutes H2O H=_____ O=_____ C8H10N4 C=_____ H=_____ N=_____ Ca(CN)2 Ca=____ C=______ N=_____ (SO4)4 S=______ O=______

Counting Atoms Coefficients Coefficient: A number YOU can place in front of a compound to change how much you have of elements within that compound. This is just like the coefficients you use in Algebra I & II Example: 4 NaCl What is the Coefficient? How many Na atoms do we have now? How many Cl atoms do we have now?

Counting Atoms Coefficients Try the following problems on your own: 4 Ag2O Ag=______ O=_______ 25 H2O H=_______ O=_______ 2 Ca3(PO4)2 Ca=______ P=_______ O=_______ 16 CO2 C=______ O=_______

Setup of the Basic Chemical Reaction When a chemical reaction takes place, it ALWAYS follows the following format: Reactants  Products What do these words mean? Reactants = your starting stuff; always located before the arrow  = yield arrow (means the reaction took place) Products = the end result; always after the arrow

Setup of the Basic Chemical Equation Notation for a Chemical Equation. A chemical equation consists of the chemical formulas of the reactants (on the left) and the products (on the right). The two are separated by an arrow symbol ("→" usually read aloud as "yields"). Each individual substance's chemical formula is separated from others by a plus sign. H2 + Br2 → HBr H2: Diatomic Hydrogen Br2: Diatomic Bromine HBr: Hydrogen Bromide Diatomic hydrogen and diatomic bromine combine to yield hydrogen bromide Written Formula

Practice 5 minutes N2 + H2 → NH3 2. Cu(NO3)2 → CuO + NO2 + O2 3. (NH4)2Cr2O7 → Cr2O3 + N2 + H2O Cr2o7= dichromate Cr2o3 = chromium (iii) oxide

Independent Practice Complete the problems on the practice sheet. I will be circulating to answer your questions. Chapter 4 Section 2 pgs. 289-297 Balancing Chemical Equations CU: #’s 1-2 C2G: #'s 1-12 Work on research IP

Balancing Chemical Equations

ANNOUNCEMENTS! Research Outline-Rough Draft: due: Feb 5 - 6 Title Page # Forming & Naming Notes 53 Forming & Naming IP (4) 54 Book Learning 55 Naming/Writing Chemical Formulas 56 Naming/Writing IP (5) 57 Balancing Equations Notes 58 Balancing Lab 59 60 Balancing IP (3) 61 ANNOUNCEMENTS! Housekeeping Rules, Door, Attention signal Tutoring – 2:15 (NO TUESDAYS) Sign log Research Outline-Rough Draft: due: Feb 5 - 6 Class website: www.kinga2.weebly.com Your classwork is homework if not finished Work can be checked ANY day/time Double check your work! Research Topic Check

Balancing Equations Now we are going to tie all of these pieces together to balance an equation so that we are obeying the Law of Conservation of Mass Steps/Rules: Make a chart to count the atoms in your reactants and your products *If an equation is unbalanced, you MAY NOT change the subscript. You are only allowed to change the coefficient out in front. Count how many atoms you have for each element in EACH compound BEFORE you start placing coefficients out in front. If you do not put a coefficient in front of a compound, we treat it as a 1.

Hg + Br2 Hg2Br2 Hg Br Guided Practice Nothing else in the equation can be changed other than the coefficient.

Guided Practice FeCl3 + MgO Fe2O3 + MgCl2 Fe Cl Mg O

Li H PO4 Li + H3PO4 H2 + Li3PO4 Guided Practice The phosphate group (like many of the polyatomic ions) remains together when balancing chemical equations.