conservation law of matter


Law of conservation of matter

The law state that matter cannot be created nor destroy in the process of chemical reaction.

Source: File:Combustion reaction of methane.jpg –

What these law is telling us is that we cannot create atom or can we destroy it. That simple tell us that the number of atom which participate in chemical reaction on the reactant side must be equal to the number atoms on the product side, that what is known as balance chemical equation. The example are shown below;

HBr + AgNO3 -> AgBr + HNO3

Reactant product

|H | Br | Ag | N| O| |H | Br | Ag | N| O|

|1 | 1 | 1 |1 | 3| |1 | 1 | 1 |1 | 3|

If we look at the above equation we can see that the number of atom of the reactant is proportional to the number of atom of the product side, as such we can conclude that no atom is created or destroy.

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Another example is shown below

2KCLO3 MnO2 2KCL + 3O2

Reactant -> product


|K | CL | O| |K | CL | O|

|2 |2 | 6 | |2 |2 | 6 |

Note: the MnO2 act as a catalyst, a catalyst is any substance that faster the rate of chemical reaction of which itself did not take part in the reaction. So it mean that the reaction was heated. So on the last illustration we can see that the number of K, CL, and O of the reactant on left hand is equal to the number of the product form on the right side of the equation.

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The law of conservation of matter can also be verify by measuring a known masses of reactants. Now let take these practical work as an example;

Take 10cm3 of silver trioxonitrate (V), AgNO3, and 10cm3 of hydrochloric acid, HCL. Take weigh of the two product and them mixed them together. Leave it for sometimes and weigh the products. On the reaction, the following masses were obtained.

  1. Mass of beaker + empty test tube = 61.0g
  2. Measure 10cm3 of AgNO3 in the beaker and 10cm3 of HCL, in the test tube.
  3. Weigh both
  4. Mixed the two and reweigh it

Mass of reactant AgNO3 + HCL + vessel = 80.8g

Mass of product AgCL + HNO3 + vessel = 80.8g

Therefore the mass of product = (80.8 – 61.0)g = 19.8g

Therefore the mass of reactant = (80.8 – 61.0)g = 19.8g

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On these practical work, we observe that both the reactant and the product have equal masses which is 19.8g, as such we can conclude that no matter was created and none was destroyed. Below is the chemical equation

AgNO3 + HCL -> AgCL + HNO3

Note: 10cm3 of both AgNO3 and HCL is taken for the sake of convenience.

These reaction was adopted because one of the products AgCL is white in colour, so changing of colour from colourless solution to white precipitate reveal that a chemical reaction has taken place.

The application of the law of conservation of matter has open way mostly in the area of chemical reaction because all balance of chemical equation is expected to conform with these law.


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