Endothermic Reactions Explained
An endothermic reaction is a type of chemical reaction that absorbs energy, usually in the form of heat, from its surroundings. This absorption of energy causes the temperature of the surroundings to decrease. In contrast, exothermic reactions release energy into the surroundings.
We need to identify which of the given reactions is endothermic. Let's analyze each option:
Reaction Analysis: Option 1 - Methane Combustion
The reaction provided is:
This reaction appears to represent the combustion of methane (\(CH_4\)). Although the products listed (\(CO_2 (g) + 2O_2 (g)\)) seem unconventional (typically it should be \(CO_2 (g) + 2H_2O (g)\)), combustion reactions, where a substance reacts rapidly with oxygen, are almost always exothermic. They release significant amounts of energy as heat and light.
Reaction Analysis: Option 2 - Glucose Respiration
The reaction provided is:
This equation represents the aerobic respiration of glucose (\(C_6H_{12}O_6\)). This biological process breaks down glucose in the presence of oxygen to produce carbon dioxide and water. Respiration is a fundamental metabolic process that releases energy for living organisms and is highly exothermic.
Reaction Analysis: Option 3 - Ammonia Synthesis
The reaction provided is:
This is the Haber-Bosch process for the synthesis of ammonia (\(NH_3\)) from nitrogen (\(N_2\)) and hydrogen (\(H_2\)). This reaction is known to be exothermic, releasing heat when ammonia is formed.
Reaction Analysis: Option 4 - Lead Nitrate Decomposition
The reaction provided is:
This reaction describes the thermal decomposition of solid lead(II) nitrate (\(Pb(NO_3)_2\)) into solid lead(II) oxide (PbO), nitrogen dioxide gas (\(NO_2\)), and oxygen gas (\(O_2\)). Decomposition reactions, especially those involving the breakdown of nitrates upon heating, typically require energy input (heat) to occur. Therefore, this is an endothermic process, as it absorbs heat from the surroundings.
| Reaction Option | Description | Energy Change |
|---|---|---|
| 1 | Methane Combustion (Assumed) | Exothermic |
| 2 | Glucose Respiration | Exothermic |
| 3 | Ammonia Synthesis (Haber Process) | Exothermic |
| 4 | Lead Nitrate Decomposition | Endothermic |
Based on the analysis, the decomposition of lead(II) nitrate is the endothermic reaction among the choices.
Important Questions from Chemical Reactions
Which one of the following nitrogen oxides may dimerize?
The chemical formula of glucose is C6H12O6. The weight % of carbon in glucose is:
For a chemical reaction with rise in temperature by 10°, the rate constant becomes nearly ____________________.
A chemical reaction in which the rate of reaction is directly proportional to the first power of the concentration of the reacting substance is called:
What is the product formed when zinc and sulphuric acid react?
