this has to do with endothermic reaction?

Question

one of the materials were use in the experiment was copper carbonate,so tell me...why does copper carbonate need to be heated in order to decompose?
Second, why does burning magnesium produce so much heat?
pls answ A.S.A.P..

Answer 1

Copper carbonate is quite stable at room temperature.
Copper carbonate decomposes at high temperatures, giving off carbon dioxide and leaving copper(II) oxide.

CuCO3(s) ---> CuO(s) + CO2(g)

According to the thermodynamic criterion of spontaneity;
this reaction has a positive value of Gibbs energy and positive entropy ,hence is spontaneous at high temperatures.
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For Magnesium;

2Mg + O2 ---> 2MgO

This reaction has a negative value of Gibbs energy and positive entropy ,hence is spontaneous at all temperatures.
Enthalpy change is negative implying that reaction is highly exothermic.

Answer 2

What you require is very specific. I will give you some hints with which you can pick up from:

1. the term ' endothermic' means that energy or heat must go into a reacting chemical system from the surroundings like the water medium or the test-tube that holds the system
2. if heat or energy enters the system from the water or the test-tube, the latter will become 'colder' as heat is taken away and the temperature of the surroundings drops. However this does not mean that the reacting substance become hotter although its energy content (enthalpy) increases.
3. With regards to copper carbonate, the heat can enter the green copper cabonate solid from a bunsen burner and the heat decomposes it to black copper (II) oxide solide and carbon dioxide
4. In this case, the total energy content (enthalpy) of copper (II) oxide and gaseous carbon dioxide is MORE than copper (II) carbonate.

The burning of magnesium is the opposite to the above. It is an EXOTHERMIC reaction as heat is given to the surroundings. However the burning of magnesium needs a little activation energy before the energy content in magnesium can be released, and the product formed is magnesium oxide which has a much lower energy content.

I like the questions your Chemistry teacher asked your class.

Answer 3

Both have a similar answer. The more stable a compound is, the lower an energy state that it is in. In order to decompose it, it's energy state must be raised, by adding heat. That is the copper carbonate. Therefore it is endothermic.
Magnesium is less stable in it's mettallic state than as magnesium oxide (oxygen from air). After a small activation energy (disrupting the weak bonds of metallic magnesium) it readily reacts with oxygen
forming a more stable compound and being quite exothermic, even giving off white and ultraviolet light
because magnesium oxide is in a much lower energy state than metallic magnesium, and energy must be radiated to reach this lower state.
To obtain metallic magnesium by reduction, electrons must be pumped in and much heat supplied to separate the magnesium and oxygen, so it is endothermic.
Chemical reactions are reversible, but the conditions for reduction and oxidation are opposite.
Okay?

Answer 4

probably cos the bonding in the molecule is very strong so some amount of initial heat is needed to make the molecule undergo any chemical change