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4 . 1 Balancing EquationsA alanced chemical equation r e f l e c t s the law o f c o n s e r v a t i o n o fmass. A alanced chemical equation has an equal number o feach k i n d of atom on b o t h sides o f the r e a c t i o n both sides o f thearrow~ nd t h e r e f o r e an equal m ass on b o t h s i d e s .Balancing an equation m e a n s o add a c o e f f i c i e n t s numbers) nf r o n t of each formula. These numbers, or c o e f f i c i e n t s representh o w many f each atom, molecules or formula u n i t s are present nthe r e a c t i o n .

NOTE:Some k e l e t o n equations are already balanced bypure coincidence.i e C 02~O2

Exa m pl e2Hg0 ~ g~ ~2 Even though the 1 i s

t h e r e chemists d o notc o e f f i c i e n t s w r i t e t

YOU CAN ONLYADD NUMBERS N FRONT OFACHEMICALFORMULA.YOU CANNOT CHANGE THE NUMBER OFINDIVIDUAL ATOMS N THECOMPOUND.

Yes: 1 FeS / 2HC1 \~ 1 FeCl2 H2SNo: 1 FeS \ H2C12 ~ 1 FeCl2 H2S

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Countina Atoms

1 CuNO3)2 +2K(OH) 1 CuOH)2 + KNO~ ~O oT ~ ~ T ` ~ ~ ~ ~

e f t Side Right SideCu=1 K=2 Cu=1 K=2N 2 =2 N =26 H =2 =2 =6NO OH =2 OH =2 NO =6

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4 . 1 S t e a m s for Balancing Chemical_~uations1 Write out the s k e l e t o n e q u a t i o n . Make sure a l l the

chemical formulas are w r i t t e n c o r r e c t l y2 Begin by b a l a n c i n g the atoms t h a t occur in the

l a r g e s t number o n b o t h sides o f the equation. Leavehydrogen, oxygen and any o t h e r elements u n t i l l a t e r .

3 Balance any polyatomic ions t h a t occur o n b o t h sidesof the equation as a whole.i . e . SO4 2 is kept as 1 SO4 2 u n i t n o t 1 S tom and 4atoms

4 alance any other element t h a t occurs in i t suncombined s t a t e ( i . e . Na or C 1 2 )

5 Balance any hydrogen atoms. Balance oxygen atomst h a t occur in a combined and an uncombined s t a t e .i . e . Combined =CO2 Uncombined =0202 an be balanced u s i n g a f r a c t i o n .

6 heck your answer. Count the number o f each typeof atom o n b o t h sides of the e q u a t i o n .

7 l l c o e f f i c i e n t s used must be in t h e i r lowest terms.** * Balancing r e a c t i o n s is a r i a l and e r r o r process** *

* **USE A PENCIL** *

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Balancing Reaction EquationsBalance the f o l l o w i n g equations:_FeS _HCI ~ _FeCl2 _H2S

_AI _H2SO4 Al2 SO4)3 _H2

_CZHs _OZ _COZ _H20

_KC103 energy _KCI _ 2

_KMn04 _HCI ~ _MnCl2 _KCI _H20 _C12

_NaCI _Mn02 2SO4 Na2SO4 _MnSO4 _H20 _C12

Cu _HNO3 ~ _Cu NO3)2 _H20 _NO2

_C3H5 OH)3 _HNO3 3H5~NO3~3 _HOH

_Na202 _H20 _NaOH _ 2

_Na2S203 _12 _Nal _Na2S406

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Please w r i t e the word e q u a t i o n and balanced chemical e q u a t i o n f o r t h ef o l l o w i n g r e a c t i o n s :

2)_AI

3)_N 3

_Fe203

_p

C ~

C`

_A1203 _Fe

_NO _H20

4)Na20 NH4)2SO4 ~ _Na2SO4 H2O _NH3

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Balancing Reaction Eauations 2AS4Sg + _~ AS4Og S 2AsCl3 + _H2S ~_As2S3 + _HCI

_NaOH + _H3PO4~_Na3PO4 + _H20_KOH + _S02 ~_K2S03 + _H20_KC103 + _HCI ~ + _H20 + _C12KCI_Pb(C2H302)2 + _(NH4)ZS ~ _PbS + _NH4C2H302_AI + _H2SO4 ~ _Al2(SO4)3 + _H20 + _S02_AI2(CO3)3 + _H20 ~ _AI(OH)3 + CO2_KC103 +energy ~_KCI + _ 2

Nal + Mn02 +_Na2SO4 +

H2SO4_MnSO4 H2 + 12

_Na2CO3 + _FeCl3 + _H20 ~_Fe OH)3 + _NaCI + _CO2