Balancing equations

Count the atoms 4 Al2(SO3)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 cannot be created or destroyed Meaning, the number of atoms each element has MUST be equal on both sides of the equation What goes in must go out!

Chemical equations MUST be balanced! Why? Because….. In balancing equations, you cannot change the subscripts! If you change the subscript, you change the substance

So how do you make #’s work if you cannot change them? You add numbers called COEFFICIENTS * A coefficient is added in FRONT of the compound ONLY, and it distributes to ALL the elements in the compound

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