PRASHANT KIRAD
Chemical Reactions and Equations Kuch important terms:
→Precipitate: Insoluble solid formed after a
Chemical Reaction: The transformation of chemical substance
into another chemical substance. e.g. Rusting of iron, the setting chemical reaction.
of milk into curd. →Exothermic Reaction: Reaction releasing heat
Chemical Equation: Representation of chemical reaction using energy.
symbols and formulae of the substances. →Endothermic Reaction: Reaction absorbing heat
Reactant A+B →C+D Product energy.
→Catalyst: Speeds up a reaction without being
Reactant Mg + O2 → MgO Product
consumed.
Characteristic Example Reaction Balanced Chemical Equation: Number of atoms of each
element in reactants = number of atoms of each element
Change in Colour Fe + CuSO₄(Blue) → FeSO₄(Blue-green) + Cu in products. Law of Conservation of Mass: Mass of
reactants = Mass of products
Change in
CaO + H₂O → Ca(OH)₂ + Heat (heat is generated) Balance these: Fe + H₂O → Fe₃O₄ + H₂
Temperature
C₆H₁₂O₆ + O₂ → CO₂ + H₂O
Change in State H₂(g) + O₂(g) → H₂O(l) (i.e., gas to liquid) Draw boxes around formulas.
Count atoms on both sides.
Evolution of Gas Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g) Start with the biggest compound.
Balance elements one by one.
Formation of Use smallest whole numbers.
Pb(NO₃)₂(aq) + KI(aq) → PbI₂(s) + KNO₃(aq)
Precipitate
Recheck for balance.
Endothermic Types of Chemical Reactions:
CaCO₃ + Heat → CaO + CO₂ (photosynthesis also)
Reaction
1.Combination Reaction: Two or more reactants
combine to form single products.
Exothermic CaO + H₂O → Ca(OH)₂ + Heat (digestion and
Reaction respiration also)
A + B → AB
The most effective way to test for CO₂ is to bubble the 3.Displacement Reaction: a more reactive element
gas through lime water, which is a diluted solution of displaces a less reactive element from its compound.
calcium hydroxide. Single Displacement A + BC → AC + B
2.Decomposition Reaction: A single reactant
decomposes to form two or more products. Double Displacement AB + CD → AD + CB
AB → A + B
Reaction Observation
Thermal Decomposition CaCO₃ → CaO + CO₂ Mg + O₂ → MgO Magnesium ribbon burns with a
(thermal energy) dazzling white flame and forms a
white powder (magnesium oxide).
Photolytic Decomposition 2AgBr → 2Ag + Br₂ Yellow precipitate of lead
(energy from sunlight) black & white photography
Pb(NO₃)₂ + KI → PbI₂
iodide forms, and the solution
Electrolytic Decomposition 2H₂O → 2H₂ + O₂ changes from colorless to
electrical energy) yellow.
Zn + H₂SO₄ → ZnSO₄ + H₂ Bubbles of hydrogen gas
form around the zinc
Hydrogen (cathode) will metal. Heat is released
produce a popping sound
during the reaction.
when a burning candle is
CaO + H₂O → Ca(OH)₂ Calcium oxide reacts
brought close.
Oxygen (anode) will vigorously with water to
make the flame of the produce slaked lime, releasing
candle burn brighter. a large amount of heat.
2FeSO₄ → Fe₂O₃ + SO₂ + SO₃ Initially green; turns
white, then brown
(ferric oxide) with the
smell of burning sulfur.
Chemical Reactions and Equations Kuch important terms:
→Precipitate: Insoluble solid formed after a
Chemical Reaction: The transformation of chemical substance
into another chemical substance. e.g. Rusting of iron, the setting chemical reaction.
of milk into curd. →Exothermic Reaction: Reaction releasing heat
Chemical Equation: Representation of chemical reaction using energy.
symbols and formulae of the substances. →Endothermic Reaction: Reaction absorbing heat
Reactant A+B →C+D Product energy.
→Catalyst: Speeds up a reaction without being
Reactant Mg + O2 → MgO Product
consumed.
Characteristic Example Reaction Balanced Chemical Equation: Number of atoms of each
element in reactants = number of atoms of each element
Change in Colour Fe + CuSO₄(Blue) → FeSO₄(Blue-green) + Cu in products. Law of Conservation of Mass: Mass of
reactants = Mass of products
Change in
CaO + H₂O → Ca(OH)₂ + Heat (heat is generated) Balance these: Fe + H₂O → Fe₃O₄ + H₂
Temperature
C₆H₁₂O₆ + O₂ → CO₂ + H₂O
Change in State H₂(g) + O₂(g) → H₂O(l) (i.e., gas to liquid) Draw boxes around formulas.
Count atoms on both sides.
Evolution of Gas Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g) Start with the biggest compound.
Balance elements one by one.
Formation of Use smallest whole numbers.
Pb(NO₃)₂(aq) + KI(aq) → PbI₂(s) + KNO₃(aq)
Precipitate
Recheck for balance.
Endothermic Types of Chemical Reactions:
CaCO₃ + Heat → CaO + CO₂ (photosynthesis also)
Reaction
1.Combination Reaction: Two or more reactants
combine to form single products.
Exothermic CaO + H₂O → Ca(OH)₂ + Heat (digestion and
Reaction respiration also)
A + B → AB
The most effective way to test for CO₂ is to bubble the 3.Displacement Reaction: a more reactive element
gas through lime water, which is a diluted solution of displaces a less reactive element from its compound.
calcium hydroxide. Single Displacement A + BC → AC + B
2.Decomposition Reaction: A single reactant
decomposes to form two or more products. Double Displacement AB + CD → AD + CB
AB → A + B
Reaction Observation
Thermal Decomposition CaCO₃ → CaO + CO₂ Mg + O₂ → MgO Magnesium ribbon burns with a
(thermal energy) dazzling white flame and forms a
white powder (magnesium oxide).
Photolytic Decomposition 2AgBr → 2Ag + Br₂ Yellow precipitate of lead
(energy from sunlight) black & white photography
Pb(NO₃)₂ + KI → PbI₂
iodide forms, and the solution
Electrolytic Decomposition 2H₂O → 2H₂ + O₂ changes from colorless to
electrical energy) yellow.
Zn + H₂SO₄ → ZnSO₄ + H₂ Bubbles of hydrogen gas
form around the zinc
Hydrogen (cathode) will metal. Heat is released
produce a popping sound
during the reaction.
when a burning candle is
CaO + H₂O → Ca(OH)₂ Calcium oxide reacts
brought close.
Oxygen (anode) will vigorously with water to
make the flame of the produce slaked lime, releasing
candle burn brighter. a large amount of heat.
2FeSO₄ → Fe₂O₃ + SO₂ + SO₃ Initially green; turns
white, then brown
(ferric oxide) with the
smell of burning sulfur.
