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. NI3 _______________________________

2. Ca(OH)2 _______________________________

3. Fe2(SO4)3.H2O _______________________________

4. (NH4)2C2O4 _______________________________

5. Co3(PO4)2.8H2O_______________________________

6. H3PO4 _______________________________

7. HClO2 _______________________________

8. N3O _______________________________

9. HI _______________________________10. Mg3P2 _______________________________

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 changes2. Temperature changes3. A gas is produced4. A precipitate (solid form

Chemical Reactions

• Occur when new substances are createdreactants products

Can be written as:• A word equation:

nitrogen monoxide + oxygen nitrogen dioxide• A symbolic equation:

2NO(g) + O2(g) 2NO2(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 + O2 K2O

Symbolic Equations

2NO(g) + O2(g) 2NO2(g)

Coefficients – indicate ratio of cmpdsState 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 + O2 2K2O

HgO Hg + O2

Helpful hints

1. Balance metals first2. Count polyatomic groups as 1 atom3. Balance oxygen atoms last4. Odd/even problem? Double it!

____Mg + ____HCl → ____MgCl2 + ____H2

____H2 + ____ N2 → ____ NH3

____ Fe + ____ Br2 → ____ FeBr3

TRY THESE!____Sn(NO 2)4 ___K3PO4 → ___KNO2 ___Sn3(PO4)4

____P4 + ____I2 → ____PI3

____Al + ____O2 → ____Al2O3

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