Chemical reactions and eq

Question 1

Oxidiation..reduction

Answer 1

Oxidation reduction
Gains oxygen loses hydrogen – oxidation
Loses oxygen gains hydrogen – reduction

OIL - RIG

Question 2

What is precipitation reaction…example

Answer 2

Any reaction which produces a precipitate is called precipitation reaction. Insoluble substance is called precipitate.
AB + CD  CB + AD
A and C cations (positive), B and D anions (negative)
Na2SO4 (aq) + BaCl2 (aq) → BaSO4 (s) + 2NaCl (aq)

Question 3

What is double displacement reaction…

Answer 3

Double displacement – Reactions in which ions are exchanged bw 2 reactants forming new compounds.

Question 4

What is displacement reaction…example

Answer 4

1. Displacement Reaction – When a more reactive element displaces a lesser reactive element from a compound.
   A + BC  AC + B
   Displacement only takes place if A is more reactive than B
   Eg Fe(s) + CuSO4 (aq) → FeSO4 (aq) + Cu(s)

Question 5

What is endothermic reaction…example

Answer 5

Energy is absorbed
Photosynthesis

Question 6

What is photolytic dec? Example…what is used for?

Answer 6

Dec bcuz of sunlight
2AgCl(s) Sunlight → 2Ag(s) + Cl2 (g)
Black and white photography

Question 7

What is thermal decomposition give example

Answer 7

Decomposition reaction carried out by heating
CaC03 –> Ca0 + Co2
Brown fumes - N02
2Pb(N03)2 –> 2Pb0 + 4N02 + 02

Question 8

Explain why Ca0 is important …what happens calcium carbonate decomposes?

Answer 8

calcium oxide is used for whitewashing walls, reacts with CO2 in the air to form calcium carbonate
CaCO3  CaO + CO2
Imp decomposition used in industries. Calcium Oxide is called quick lime and is used in manufacture of cement

Question 9

What is decomposition reaction..give example

Answer 9

1. Decomposition Reaction – A single reactant breaks down to simpler products.
   AB  A + B
   Ferrous sulphate crystals lose water when heated and colour changes. It then decomposes to ferric oxide( Fe2O3),Sulphur dioxide(SO2) and sulphur trioxide(SO3)
   2FeSO4  Fe203 + S02 + SO3

Question 10

What is exothermic reaction ? Give example

Answer 10

Reactions which release heat along with formation of products is called exothermic reaction.
Eg: CaO(s) + H20(l) = Ca(OH)2(aq) + Heat
Burning of natural gas, decomposition of veg matter into compost, respiration

Question 11

What is combination reaction give example

Answer 11

1. Combination Reaction - A reaction in which a single product is formed from 2 or more reactants in combination reaction.
   Formation of water

Question 12

Chemical eq for photosynthesis

Answer 12

6C02 + 12H20 –> C6H1206 + 602 + 6C02

Question 13

What is a skeletal equation

Answer 13

Another name for unbalanced eq

Question 14

What are the changes involved in chemical reactions?

Answer 14

Change is temp, colour, state
Evolution of gas and formation of precipitate