#45 Balancing equations notes

Count the atoms 4 Al(OH)3 3(NH3)3(PO4)2

Chemical Equation Vocab 2H2 + O2  2H2O Coefficient – a # that is in front of the element or compound and distributed to ALL associated elements or compounds Subscript – identifies the amount of atoms in an element Reactant(s) – the starting material in a chemical reaction (on the left) Product(s) – the substance formed from the chemical reactants ( on the right) Yield – like a equal sign; separates the products from the reactants

*Law of conservation of mass/matter The Law of Conservation of Mass/Matter states that matter cannot be created or destroyed Meaning, the number of atoms each element has MUST be equal on both sides of the chemical equation A way to remember this is: What goes in must come out

Chemical equations MUST be balanced! Why? Because the Law of Conservation of Mass or Matter

So how do I balance equations? *In balancing equations, you CANNOT change the subscripts! If you change the subscript, you change the substance For example: H20 H2O2

*So how do you make #’s work if you cannot change subscripts? You change the COEFFICIENTS and recount the atoms

2 h2O = H2O + H2O How do you count the atoms on the reactant side (left side)? How about the product side (right side)?

*Rules for balancing equations (be prepared to use your eraser) Draw an line underneath the yield sign of the equation. Count ALL atoms on both sides of the equation. Pick an element that is not equal on both sides and find the least common multiple. Add coefficient to the chosen element and recount atoms Repeat steps 2 and 3 for unbalanced elements and recount atoms. (Until all elements are even) Write the balanced equation Al + O2  Al2O2 Is it balanced?

Let’s try these two together Na + Cl2  NaCl Mg + N2  Mg3N2

You try Cr + O2  Cr2O3 NH3 + O2  N2 + H2O