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1)HOW DO WE COME TO KNOW THAT A CHEMICAL REACTION HAS TAKEN PLACE? 2)IS THERE ANY OTHER SHORTER WAY FOR REPRESENTING CHEMICAL EQUATION? 3)IS THE NUMBER OF ATOMS OF EACH ELEMENT THE SAME ON BOTH THE SIDES? 4)IS THE CHEMICAL EQUATION MG+O2->MGO Balanced? 5)3FE+4H2O->FE3O4+4H2 DOES THIS EQUATION TELL US ANYTHING ABOUT THE PHYSICAL STATE OF EACH REACTANT AND PRODUCT? 6)WHY SHOULD A MAGNESIUM RIBBON BE CLEANED BEFORE BURNING IN AIR? 7) RESPIRATION IS AN EXOTHERMIC PROCESS.EXPLAIN?

(1)All chemical reactions are usually characterized by a chemical change and they yield one or more products which are different from the reactants. Thus we can know that a chemical reaction has taken place . (2)Chemical equation is a short hand representation of a chemical change or reaction in terms of symbols and formula .It gives the information about moles and masses of various reactants and products and also the volumes of gaseous reactants and products measured at S.T.P.

(3)The substances which take part in a chemical reaction-are known as reactants. Substances formed due to chemical changes are known as products .A balanced equation can be defined as a chemical equation in which number of atoms of each element is same on both the sides of a chemical reaction so the number of atoms of each element will be same on both sides ..

(4) The equation above written is not balanced .Magnesium burns in oxygen with an intense white flame to give white solid magnesium oxide .
The chemical equation for the reaction can be written as,
  2Mg +O2 ->  2MgO

(5)The physical state of reactants and products are indicated by (s) for solid ,(l) for liquid, (g) for gas and (aq) aqueous solutions .The equation written above is balanced but it doesn't tell anything about the physical state of the reactant and product .The equation can be written as
   3Fe (s) + 4H2O(l) ->Fe3O4(s) +4H2 (g)

(6) Magnesium combines with oxygen in the atmosphere to form magnesium oxide,it will change the original property of the element and also it may prevent or slow down the burning of magnesium Magnesium ribbon must be cleaned before burning to remove all the oxide coating which may have been deposited on the ribbon .

(7) Respiration is the chemical reaction which happens in our bodies to produce energy for our cells. The equation below describes what happens during this reaction:

C6H12O6 +6O2 ->6CO2 +6H2O +energy

In the reaction above, glucose (a type of carbohydrate in the food we eat) reacts with oxygen from the air that we breathe in, to form carbon dioxide (which we breathe out), water and energy. The energy that is produced allows the cell to carry out its functions efficiently.     It is not the food itself that provides you with energy, but the exothermic reaction that takes place when compounds within the food react with the oxygen you have breathed in.Energy is released during the process of respiration . Thus respiration is an exothermic reaction .


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