#52 Counting Atoms WS #53 Balancing equations notes

Description Physical or Chemical Property or change The play-do is stringy A teacher has brown hair Cotton can burn easily Water boils at 100*C Gold does not tarnish when exposed to water (H2O) The pot keeps the food warm

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? *When 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

*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 Fe + Cl2  FeCl3 Is it balanced?

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

Balance the equations Mg + N2  Mg3N2 Cr + O2  Cr2O3 NH3 + O2  N2 + H2O Na3PO4 + CaCl2  NaCl + Ca3 (PO4)2 Mg(NO3)2 + K3PO4  Mg3(PO4)2 + KNO3

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

Na3PO4 + CaCl2  NaCl + Ca3(PO4)2

extra

Bonus problem… Mg(NO3)2 + K3PO4  Mg3(PO4)2 + KNO3