In a chemical reaction (or any ordinary change in matter physical or chemical)..

Transcription

1 WARM UP Chemical Formulas/Equations ch. 14, p ) Finish the counting atoms worksheet you received at the end of class on Thursday. Then answer the questions below: 1) In ~1785, Antoine Lavoisier discovered the (LoCoM), which can be stated as: In a chemical reaction (or any ordinary change in matter physical or chemical).. 2) This law means that a chemical equation must show. (395) 3) Circle the chemical equations/diagrams below only if they follow Lavoisier s LoCoME :

2 Balancing Equations Notes: Sometimes chemical equations are not written in a balanced way. We need to correct this problem. In order to reflect the principle of conservation of mass, it is necessary to balance the equations using Coefficients. GUIDED EXAMPLE: Magnesium (Mg) reacts with Oxygen (O 2) gas forming magnesium oxide (MgO). Interpret and write the equation using chemical formulas. (if not already in equation form) List the symbols for each element underneath both sides of the equation. ***LIST THEM IN THE SAME ORDER ON BOTH SIDES, OR IT WILL GET CONFUSING!*** Count the atoms of each element on each side of the equation. Determine if equation is balanced. If the equation is not balanced, add COEFFICIENTS to the original equation and make changes to the number of each lists until both sides have the same number of each type of atom. HINTS: Focus on common denominators/multiples for coefficients. Sometimes it might be a trial and error thing! Think about what you could multiply things by. Don t think about adding, think about what you could multiply each by to make them equal. PRACTICE PROBLEMS: 1) Interpret and write the equation using chemical formulas. (if not already in equation form) List the symbols for each element underneath both sides of the equation. ***LIST THEM IN THE SAME ORDER ON BOTH SIDES, OR IT WILL GET CONFUSING!*** Count the atoms of each element on each side of the equation. Determine if equation is balanced. If the equation is not balanced, add COEFFICIENTS to the original equation and make changes to the number of each lists until both sides have the same number of each type of atom.

3 2) Sodium (Na) reacts with oxygen (O 2) gas forming sodium oxide (Na 2O) Interpret and write the equation using chemical formulas. (if not already in equation form) List the symbols for each element underneath both sides of the equation. ***LIST THEM IN THE SAME ORDER ON BOTH SIDES*** Count the atoms of each element on each side of the equation. If the equation is not balanced, add COEFFICIENTS to the original equation and make changes to the number of each lists until both sides have the same number of each type of atom. 3) Tin (Sn) reacts with chlorine (Cl 2) gas to form tin chloride (SnCl 2) Interpret and write the equation using chemical formulas. (if not already in equation form) List the symbols for each element underneath both sides of the equation. ***LIST THEM IN THE SAME ORDER ON BOTH SIDES*** Count the atoms of each element on each side of the equation. If the equation is not balanced, add COEFFICIENTS to the original equation and make changes to the number of each lists until both sides have the same number of each type of atom. For the problems below, coefficients may be added (or not added) to the blanks (not all blanks may have coefficients on them, or you can write 1 since that is the same thing as having no coefficient) 4) NaCl + BeF 2 NaF + BeCl 2 5) H 2 + N 2 NH 3 6) What does a balanced equation mean? 7) What concept does a balanced equation represent? 8) What is wrong with the following equation? 3Ca + ScF 3 3CaF 2

4 MORE BALANCING EQUATIONS! SOME WILL BE CHALLENGING! Remember, not all blanks need a coefficient. Complete the Starred (*) questions first! Show all work! 1) Na3PO4 + KOH NaOH + K3PO4 *2) MgF2 + Li2CO3 MgCO3 + LiF *3) P4 + O2 P2O3 4) RbNO3 + BeF2 Be(NO3)2 + RbF 5) AgNO3 + Cu Cu(NO3)2 + Ag *6) CF4 + Br2 CBr4 + F2 7) HCN + CuSO4 H2SO4 + Cu(CN)2 *8) GaF3 + Cs CsF + Ga *9) BaS + PtF2 BaF2 + PtS

5 *10) N2 + H2 NH3 *11) NaF + Br2 NaBr + F2 12) Pb(OH)2 + HCl H2O + PbCl2 13) AlBr3 + K2SO4 KBr + Al2(SO4)3 *14) CH4 + O2 CO2 + H2O 15) Na3PO4 + CaCl2 NaCl + Ca3(PO4)2 *16) K + Cl2 KCl *17) Al + HCl H2 + AlCl3 *18) N2 + F2 NF3 *19) SO2 + Li2Se SSe2 + Li2O