, Chemical Reactions and Equations
Definition: A chemical reaction is a process where substances
undergo a transformation to form new substances with different
properties through the breaking and formation of bonds between atoms.
Formation of hydrogen gas by the
action of dilute sulphuric acid on
zinc.
Burning of natural gas.
Burning of coal.
Formation of water from
hydrogen gas and oxygen gas.
Corrosion of iron leading to rust
formation, etc.
Evaluation of reaction
.0
Following are the 4 key parameters to evaluate the presence of a reaction:
2
Change in state
ng Change in colour Evolution of gas Change in temperature
ni
ar
L e
e →
Chemical Equations: A chemical equation is a symbolic
representation of a chemical reaction using chemical formulae A+B C+D
iv
instead of words.
t
Chemical equations symbolize reactions with formulas.
ea
Reactants change on the left (L.H.S.), products form on the right (R.H.S.).
Conditions like catalysts or temperature are noted above the arrow.
r
States like solid (s), liquid (l), and gas (g) can be added.
Unbalanced equations lack equal atoms; balanced ones have them.
C → 2Mg (s) + O₂ (g) 2MgO (s)
Balancing of Chemical equations:
Aim : Equal atoms on both sides.
Need : Law of Conservation of Mass; Mass can neither be created nor destroyed.
Unbalanced equation : Fe + H₂O → Fe₃O₄ + H₂
Subscript
Subscripts won't change (they are part of formulas)
1
Definition: A chemical reaction is a process where substances
undergo a transformation to form new substances with different
properties through the breaking and formation of bonds between atoms.
Formation of hydrogen gas by the
action of dilute sulphuric acid on
zinc.
Burning of natural gas.
Burning of coal.
Formation of water from
hydrogen gas and oxygen gas.
Corrosion of iron leading to rust
formation, etc.
Evaluation of reaction
.0
Following are the 4 key parameters to evaluate the presence of a reaction:
2
Change in state
ng Change in colour Evolution of gas Change in temperature
ni
ar
L e
e →
Chemical Equations: A chemical equation is a symbolic
representation of a chemical reaction using chemical formulae A+B C+D
iv
instead of words.
t
Chemical equations symbolize reactions with formulas.
ea
Reactants change on the left (L.H.S.), products form on the right (R.H.S.).
Conditions like catalysts or temperature are noted above the arrow.
r
States like solid (s), liquid (l), and gas (g) can be added.
Unbalanced equations lack equal atoms; balanced ones have them.
C → 2Mg (s) + O₂ (g) 2MgO (s)
Balancing of Chemical equations:
Aim : Equal atoms on both sides.
Need : Law of Conservation of Mass; Mass can neither be created nor destroyed.
Unbalanced equation : Fe + H₂O → Fe₃O₄ + H₂
Subscript
Subscripts won't change (they are part of formulas)
1
