Science 10 Chapter 4.3 Balancing Chemical Equations

Today  Learning check  Review chemical compounds and formulas  Chemical Reactions!!!

1.Silver chloride__________ 2. Sulphur dioxide__________ 3. Lead (II) acetate decahydrate_______________ 4.Silver dichromate__________ 5.Silicon tetraflouride__________ 6. Ammonium phosphate__________ 7. Copper (I) iodide__________ 8. Iron (II) fluoride nonahydrate_____________ 9. Zinc hydrogen sulphite______________ 10. Manganese (IV) monohydrogen phosphate trihydrate ________________ Name into Formula

Formula into Name 1. NI 3 _______________________________ 2. Ca(OH) 2 _______________________________ 3. Fe 2 (SO 4 ) 3. H 2 O_______________________________ 4. (NH 4 ) 2 C 2 O 4 _______________________________ 5. Co 3 (PO 4 ) 2. 8H 2 O_______________________________ 6. H 3 PO 4 _______________________________ 7. HClO 2 _______________________________ 8. N 3 O_______________________________ 9. HI_______________________________ 10. Mg 3 P 2 _______________________________

Chemical Changes Nothing is created or destroyed, only rearranged Reactants = products 200 yrs ago John Dalton realized atoms rearrange # of each atom in reactants = # of each atom in products

The LAW: Conservation of mass Antoine and Marie-Anne Lavoisier in the 1700’s Atoms are neither created or destroyed in chemical reactions Mass reactants = mass products

Indicators of chemical change 1.Colour changes 2.Temperature changes 3.A gas is produced 4.A precipitate (solid form

Chemical Reactions Occur when new substances are created reactants  products Can be written as: A word equation: nitrogen monoxide + oxygen  nitrogen dioxide A symbolic equation: 2NO(g) + O 2 (g)  2NO 2 (g)

Word equations (the simplest) Potassium metal + oxygen gas  potassium oxide Provides limited information

Skeletal Equations (Symbolic) Show formulas of compounds/elements, but not quantities of atoms e.g., K + O 2  K 2 O

Symbolic Equations 2NO(g) + O 2 (g)  2NO 2 (g) Coefficients – indicate ratio of cmpds State of matter – dissolved in water/aqueous (aq), solid (s), liquid (l), or gas (g)

Balanced chemical equation Shows all atoms and their quantities Number of each atom should be equal on both sides of the reaction arrow Always use smallest whole-number ratio To balance, change coefficients, never subscripts e.g., 4K + O 2  2K 2 O HgO  Hg + O 2

Helpful hints 1.Balance metals first 2.Count polyatomic groups as 1 atom 3.Balance oxygen atoms last 4.Odd/even problem? Double it! ____Mg + ____HCl → ____MgCl 2 + ____H 2 ____H 2 + ____ N 2 → ____ NH 3 ____ Fe + ____ Br 2 → ____ FeBr 3

____Sn(NO­ 2 ) 4 ___K 3 PO 4 → ___KNO 2 ___Sn 3 (PO 4 ) 4 ____P 4 + ____I 2 → ____PI 3 ____Al + ____O 2 → ____Al 2 O 3

Today  Learning check  Review chemical compounds and formulas  Chemical Reactions #X # (s)A  B  Due tomorrow: workbook pages 71 and 73  Due Monday: workbook pages 77, (78-79 even #’s), 80