National Chemistry

BALANCING EQUATIONS

When balancing equations you -
a) MUST end up with the same number of each atom on both sides of the arrow
b) MUST NOT change any of the formula you are given

Balance the following equation

  N2 + H2 -----------------> NH3 need 2Ns on right hand side (RHS) therefore need another NH3

  N2 + H2 -----------------> NH3
  NH3
   now need 6Hs on left hand side (LHS) therefore need more H2

  N2 + H2 -----------------> NH3
  H2 NH3 that is only 4Hs on LHS need more H2

  N2 + H2 -----------------> NH3
  H2 NH3
  H2   2 x N on both sides; 6 x H on both sides

  write correctly as

  N2 + 3 H2 -----------------> 2 NH3
 

Balance the following equation

NB oxygens appear in three chemicals so leave oxygen till last

  Fe2O3 + CO -----------------> Fe + CO2 need 2 x Fe on RHS - give a Fe

  Fe2O3 + CO -----------------> Fe + CO2
  Fe need 4 x O on RHS = give a CO2

  Fe2O3 + CO -----------------> Fe + CO2
  Fe CO2 need another C on LHS = give a CO

  Fe2O3 + CO -----------------> Fe + CO2
  CO Fe CO2 need more O on RHS = give a CO2

  Fe2O3 + CO -----------------> Fe + CO2
  CO Fe CO2
  CO2 need another C on LHS = give a CO

  Fe2O3 + CO -----------------> Fe + CO2
  CO Fe CO2
  CO CO2 2 x Fe; 3 x C and 6 x O on both sides

  write correctly as

  Fe2O3 + 3 CO -----------------> 2 Fe + 3 CO2

Find more balancing eqation questions in Credit papers

1998 - Q19 1999 - Q15 2000 - Q13 2001 - Q 12 2002 - Q12

2004 - Q17 2005 - Q 16 2006 - Q16 2007 - Q10 2008 - Q12

2009 - Q16 2010 - Q14

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