CBSE - 10                                          Chemical Reactions and EquationsChemistry                              ...
CBSE - 10                                           Chemical Reactions and EquationsChemistry                             ...
CBSE - 10                   Chemical Reactions and EquationsChemistry                      Representing a Chemical Reactio...
CBSE - 10                               Chemical Reactions and EquationsChemistry                                  Represe...
CBSE - 10                                        Chemical Reactions and EquationsChemistry                                ...
CBSE - 10                                        Chemical Reactions and EquationsChemistry                                ...
CBSE - 10                                         Chemical Reactions and EquationsChemistry                               ...
Chemical Reactions and Equations                                                      Representing a Chemical Reaction  Ba...
CBSE - 10                                         Chemical Reactions and EquationsChemistry                               ...
CBSE - 10                                         Chemical Reactions and EquationsChemistry                               ...
CBSE - 10                                          Chemical Reactions and EquationsChemistry                              ...
Chemical Reactions and Equations                                                      Representing a Chemical Reaction  Ba...
Chemical Reactions and Equations                                                     Representing a Chemical Reaction  Bal...
CBSE - 10                                            Chemical Reactions and EquationsChemistry                            ...
CBSE - 10                                           Chemical Reactions and EquationsChemistry                             ...
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Balancing chemical equation

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Balancing chemical equation

  1. 1. CBSE - 10 Chemical Reactions and EquationsChemistry Representing a Chemical Reaction Sub-topic Contents • Word equation • Symbolic representation • Balanced chemical equations • Symbolic equation with physical statesSubtopic ID: 01.02.00
  2. 2. CBSE - 10 Chemical Reactions and EquationsChemistry Representing a Chemical Reaction Word Equation This is an example of a word equation to represent the reaction between barium Barium carbonate + Phosphoric acid carbonate and phosphoric acid.  Barium phosphate + Water + Carbon dioxideSubtopic ID: 01.02.01
  3. 3. CBSE - 10 Chemical Reactions and EquationsChemistry Representing a Chemical Reaction Symbolic Representation In order to handle the number of moles of reactants and products numerically it would be convenient to represent them in a symbolic equation.Subtopic ID: 01.02.02
  4. 4. CBSE - 10 Chemical Reactions and EquationsChemistry Representing a Chemical Reaction Balanced Chemical Equations You would have watched the combustion of methane in air Combustion of Methane in any oil refinery unit. Let us write the chemical equation for this reaction. There are a few steps involved in balancing a chemical equation.Subtopic ID: 01.02.03
  5. 5. CBSE - 10 Chemical Reactions and EquationsChemistry Representing a Chemical Reaction Balanced Chemical Equations In step-1, we need to write the word equation. Methane gives carbon dioxide and Step-1 water on combustion in air. Methane + Oxygen  Carbon dioxide + WaterSubtopic ID: 01.02.03
  6. 6. CBSE - 10 Chemical Reactions and EquationsChemistry Representing a Chemical Reaction Balanced Chemical Equations Let us represent the word equation by the respective molecular formula. Step-2 CH4 + O2  CO2 + H2O Methane + Oxygen  Carbon dioxide + WaterSubtopic ID: 01.02.03
  7. 7. CBSE - 10 Chemical Reactions and EquationsChemistry Representing a Chemical Reaction Balanced Chemical Equations Write down the number of atoms present on each side of Step-3 the arrow. On the right hand side we have one carbon, four hydrogen and 2 oxygen CH4 + O2  CO2 + H2O atoms. On the right hand side we have 1 carbon, 2 hydrogen and 3 oxygen atoms. No. of atoms in No. of atoms in Element LHS RHS C 1 1 H 4 2 O 2 3Subtopic ID: 01.02.03
  8. 8. Chemical Reactions and Equations Representing a Chemical Reaction Balanced Chemical Equations The atoms are not balanced in this equation. Start balancing Step-4 from the element with the greater number of atoms. Do not give priority to the atom CH4 + O2  CO2 + H2O found in more than one compound on either side of No. of atoms in No. of atoms the arrow. For example, since oxygen is present in two Element LHS in RHS compounds on the right hand side we should not give C 1 1 priority to the oxygen atom H 4 2 when balancing. O 2 3Subtopic ID: 01.02.03
  9. 9. CBSE - 10 Chemical Reactions and EquationsChemistry Representing a Chemical Reaction Balanced Chemical Equations Balance the hydrogen atoms by multiplying by 2 on the right Step-5 hand side. CH4 + O2  CO2 + H2O No. of atoms in No. of atoms in Element LHS RHS C 1 1 H 4 2x2 O 2 3Subtopic ID: 01.02.03
  10. 10. CBSE - 10 Chemical Reactions and EquationsChemistry Representing a Chemical Reaction Balanced Chemical Equations Write out the partially balanced equation. Step-6 CH4 + O2  CO2 + 2H2O No. of atoms in No. of atoms in Element LHS RHS C 1 1 H 4 2x2 O 2 3Subtopic ID: 01.02.03
  11. 11. CBSE - 10 Chemical Reactions and EquationsChemistry Representing a Chemical Reaction Balanced Chemical Equations Write down the number of atoms present on both sides Step-7 of the arrow of the revised equation. Again check whether all the atoms are balanced. CH4 + O2  CO2 + 2H2O Step-7 No. of atoms No. of atoms in Element in LHS RHS C 1 1 H 4 4 O 2 4Subtopic ID: 01.02.03
  12. 12. Chemical Reactions and Equations Representing a Chemical Reaction Balanced Chemical Equations Balance the atoms of the remaining elements, here Step-8 oxygen. CH4 + O2  CO2 + 2H2O Step-7 No. of atoms No. of atoms in Element in LHS RHS C 1 1 H 4 4 O 2x2 4Subtopic ID: 01.02.03
  13. 13. Chemical Reactions and Equations Representing a Chemical Reaction Balanced Chemical Equations Write down the balanced equation. Step-9 CH4 + 2O2  CO2 + 2H2O No. of atoms No. of atoms in Element in LHS RHS C 1 1 H 4 4 O 2x2 4Subtopic ID: 01.02.03
  14. 14. CBSE - 10 Chemical Reactions and EquationsChemistry Representing a Chemical Reaction Symbolic Equation with Physical States We can also mention the states of reactants and products within brackets. The subscripts g, l, s represent gas, liquid and solid respectively. CH4(g) + 2O2(g)  CO2(g) + 2H2O(l) g – gaseous state l – liquid stateSubtopic ID: 01.02.04
  15. 15. CBSE - 10 Chemical Reactions and EquationsChemistry Representing a Chemical Reaction Symbolic Equation with Physical States We can write the reaction condition above the arrow mark. Here, the reaction needs heating. This is indicated by a small triangle. CH4(g) + 2O2(g) Δ CO2(g) + 2H2O(l) = HeatSubtopic ID: 01.02.04

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