Balancing Reactions

What is the difference between a chemical and physical change? What is some evidence you might observe to know a chemical change has taken place?

Chemical Reactions Process by which the atoms of one or more substances are rearranged to form different substances What is some evidence you might observe to know that a chemical reaction has taken place?

What’s Involved 2 H2 (g) + O2 (g)  2 H2O (l) Reactant – starting substance Product – substances formed in the reaction +  ⇌ (s), (l), (g), (aq)

Word Equations Word Equation Skeleton Equation Aluminum (s) + bromine (l)  aluminum bromide (s) Skeleton Equation Al (s) + Br2 (l)  AlBr3 (s)

Write the Skeleton Equations Hydrogen (g) + bromine (g)  hydrogen bromide (g) H2 (g) + Br2 (g)  HBr (g) Carbon monoxide (g) + oxygen (g)  carbon dioxide (g) CO (g) + O2 (g)  CO2 (g) Challenge: When heated solid potassium chlorate yields solid potassium chloride and oxygen gas. Potassium chlorate (s)  potassium chloride (s) + oxygen(g) KClO3 (s)  KCl (s) + O2 (g)

Chemical Equations Chemical Equation Statement that uses chemical formulas to show identities and relative amounts of the substances involved in a chemical reaction

Balancing Chemical Equations Determine the reactants and products. Write the formula for each reactant and product and tell its state of matter Start with the reactants and count the total number of atoms present on each side Determine which of the compounds need coefficients to balance both sides of the equation Coefficient – the number written in front of a reactant or product Double check your work

Balance __Na3PO4 (aq) + __KOH (aq)  __NaOH (aq) + __ K3PO4 (s) __MgF2 (aq) + __Li2CO3 (aq)  __MgCO3 (s) + __LiF (aq) MgF2 (aq) + Li2CO3 (aq)  MgCO3 (s) + 2 LiF (aq) __P4 (g) + __ O2 (g)  __ P2O3 (g) P4 (g) + 3 O2 (g)  2 P2O3 (g)

What are the steps for balancing a chemical Equation? Balance the equation below. __VO(s) + __ Fe2O3 (s) __ FeO (s) + __ V2O5 (s) 2 VO(s) + 3 Fe2O3 (s) 6 FeO (s) + 1 V2O5 (s)

Word Equations Solid zinc and lead (II) nitrate solution react to form zinc nitrate solution and solid lead. Aluminum bromide solid and chlorine gas react to form aluminum chloride solid and bromine gas. Potassium metal and chlorine gas combine to form solid potassium chloride. Calcium hydroxide solution and phosphoric acid react to form calcium phosphate solid and water.

Answers Zn (s) + Pb(NO3)2 (aq)  Zn(NO3)2 (aq) + Pb (s) 2 AlBr3 (s) + 3 Cl2 (g)  2 AlCl3 (s) + 3 Br2 (g) 2 K (s) + Cl2 (g)  2 KCl (s) 3 Ca(OH)2 (aq) + 2 H3PO4 (aq)  Ca3(PO4)2 (s) + 6 H2O (l)