Which Reaction Is Exothermic?A. C H 4 + 2 O 2 → C O 2 + 2 H 2 O + 891 KJ CH_4 + 2 O_2 \rightarrow CO_2 + 2 H_2O + 891 \text{ KJ} C H 4 ​ + 2 O 2 ​ → C O 2 ​ + 2 H 2 ​ O + 891 KJ B. N H 4 N O 3 + H 2 O + 25 KJ → N H 4 + ( A Q ) + N O 3 − ( A Q NH_4NO_3 + H_2O + 25 \text{ KJ} \rightarrow NH_4^{+}(aq) + NO_3^{-}(aq N H 4 ​ N O 3 ​ + H 2 ​ O + 25 KJ → N H 4 + ​ ( A Q ) + N O 3 − ​ ( A Q ]C. 2 H 2 O + 286 KJ → 2 H 2 + O 2 2 H_2O + 286 \text{ KJ} \rightarrow 2 H_2 + O_2 2 H 2 ​ O + 286 KJ → 2 H 2 ​ + O 2 ​ D.

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In chemistry, an exothermic reaction is a type of chemical reaction that releases heat energy into the surroundings. This type of reaction is often characterized by a negative change in enthalpy (ΔH), which indicates that the reaction is releasing energy. In this article, we will examine four different chemical reactions and determine which one is exothermic.

What is an Exothermic Reaction?

An exothermic reaction is a chemical reaction that releases heat energy into the surroundings. This type of reaction is often accompanied by a decrease in temperature, as the heat energy is transferred from the reaction to the surroundings. Exothermic reactions can be classified into two main categories: combustion reactions and decomposition reactions.

Combustion Reactions

Combustion reactions are a type of exothermic reaction that involves the reaction of a fuel with oxygen to produce heat and light. Examples of combustion reactions include the burning of gasoline, the combustion of wood, and the burning of natural gas. Combustion reactions are often highly exothermic, releasing large amounts of heat energy into the surroundings.

Decomposition Reactions

Decomposition reactions are a type of exothermic reaction that involves the breakdown of a compound into simpler substances. Examples of decomposition reactions include the decomposition of hydrogen peroxide (H2O2) into water (H2O) and oxygen (O2), and the decomposition of ammonium nitrate (NH4NO3) into ammonia (NH3) and nitric acid (HNO3). Decomposition reactions can be highly exothermic, releasing large amounts of heat energy into the surroundings.

Examples of Exothermic Reactions

Let's examine four different chemical reactions and determine which one is exothermic.

Reaction A: Combustion of Methane

CH4+2O2→CO2+2H2O+891 kJCH_4 + 2 O_2 \rightarrow CO_2 + 2 H_2O + 891 \text{ kJ}

This reaction is a combustion reaction, where methane (CH4) reacts with oxygen (O2) to produce carbon dioxide (CO2) and water (H2O). The reaction releases 891 kJ of heat energy into the surroundings, indicating that it is an exothermic reaction.

Reaction B: Decomposition of Ammonium Nitrate

NH4NO3+H2O+25 kJ→NH4+(aq)+NO3−(aq)NH_4NO_3 + H_2O + 25 \text{ kJ} \rightarrow NH_4^{+}(aq) + NO_3^{-}(aq)

This reaction is a decomposition reaction, where ammonium nitrate (NH4NO3) reacts with water (H2O) to produce ammonium ions (NH4+) and nitrate ions (NO3-). The reaction releases 25 kJ of heat energy into the surroundings, indicating that it is an exothermic reaction.

Reaction C: Combustion of Hydrogen

2H2O+286 kJ→2H2+O22 H_2O + 286 \text{ kJ} \rightarrow 2 H_2 + O_2

This reaction is a combustion reaction, where hydrogen (H2) reacts with oxygen (O2) to produce water (H2O). The reaction releases 286 kJ of heat energy into the surroundings, indicating that it is an exothermic reaction.

Reaction D: None of the Above

This reaction is not an exothermic reaction.

Conclusion

Based on the analysis of the four chemical reactions, we can conclude that Reaction A, Reaction B, and Reaction C are exothermic reactions. Reaction A is a combustion reaction that releases 891 kJ of heat energy into the surroundings, while Reaction B is a decomposition reaction that releases 25 kJ of heat energy into the surroundings. Reaction C is also a combustion reaction that releases 286 kJ of heat energy into the surroundings.

Key Takeaways

  • An exothermic reaction is a type of chemical reaction that releases heat energy into the surroundings.
  • Combustion reactions and decomposition reactions are two main categories of exothermic reactions.
  • Exothermic reactions can be highly energetic, releasing large amounts of heat energy into the surroundings.
  • The analysis of four chemical reactions has shown that Reaction A, Reaction B, and Reaction C are exothermic reactions.

References

  • Atkins, P. W., & De Paula, J. (2010). Physical chemistry (9th ed.). Oxford University Press.
  • Chang, R. (2010). Chemistry: The central science (11th ed.). McGraw-Hill.
  • Petrucci, R. H., Harwood, W. S., & Herring, F. G. (2011). General chemistry: Principles and modern applications (10th ed.). Pearson Education.
    Exothermic Reactions: Frequently Asked Questions =====================================================

In our previous article, we discussed the concept of exothermic reactions and examined four different chemical reactions to determine which ones are exothermic. In this article, we will answer some frequently asked questions about exothermic reactions.

Q: What is the difference between an exothermic reaction and an endothermic reaction?

A: An exothermic reaction is a type of chemical reaction that releases heat energy into the surroundings, while an endothermic reaction is a type of chemical reaction that absorbs heat energy from the surroundings. In other words, an exothermic reaction is a reaction that releases energy, while an endothermic reaction is a reaction that requires energy.

Q: What are some examples of exothermic reactions?

A: Some examples of exothermic reactions include:

  • Combustion reactions, such as the burning of gasoline or wood
  • Decomposition reactions, such as the decomposition of hydrogen peroxide (H2O2) into water (H2O) and oxygen (O2)
  • Neutralization reactions, such as the reaction between acid and base
  • Oxidation reactions, such as the reaction between a metal and oxygen

Q: What are some examples of endothermic reactions?

A: Some examples of endothermic reactions include:

  • Melting of ice
  • Boiling of water
  • Dissolution of a solid in a solvent
  • Combustion of a fuel in a combustion engine

Q: How can I determine if a reaction is exothermic or endothermic?

A: To determine if a reaction is exothermic or endothermic, you can use the following methods:

  • Measure the temperature change of the reaction
  • Measure the heat energy released or absorbed by the reaction
  • Use a calorimeter to measure the heat energy released or absorbed by the reaction
  • Use a thermocouple to measure the temperature change of the reaction

Q: What are some safety precautions I should take when working with exothermic reactions?

A: When working with exothermic reactions, you should take the following safety precautions:

  • Wear protective clothing, including gloves and safety glasses
  • Work in a well-ventilated area
  • Use a heat-resistant container to prevent the reaction from getting out of control
  • Have a fire extinguisher nearby in case of an emergency
  • Follow proper laboratory procedures and protocols

Q: Can exothermic reactions be used for practical applications?

A: Yes, exothermic reactions can be used for practical applications, such as:

  • Generating heat for cooking or heating
  • Producing electricity through the use of fuel cells
  • Propelling vehicles through the use of combustion engines
  • Treating wastewater through the use of oxidation reactions

Q: What are some common mistakes to avoid when working with exothermic reactions?

A: Some common mistakes to avoid when working with exothermic reactions include:

  • Not wearing protective clothing or safety glasses
  • Not working in a well-ventilated area
  • Not using a heat-resistant container
  • Not following proper laboratory procedures and protocols
  • Not having a fire extinguisher nearby in case of an emergency

Conclusion

Exothermic reactions are an important topic in chemistry, and understanding how to identify and work with them is crucial for many practical applications. By following the safety precautions and guidelines outlined in this article, you can safely and effectively work with exothermic reactions.

Key Takeaways

  • Exothermic reactions release heat energy into the surroundings
  • Endothermic reactions absorb heat energy from the surroundings
  • Exothermic reactions can be used for practical applications, such as generating heat or producing electricity
  • Safety precautions should be taken when working with exothermic reactions, including wearing protective clothing and working in a well-ventilated area.

References

  • Atkins, P. W., & De Paula, J. (2010). Physical chemistry (9th ed.). Oxford University Press.
  • Chang, R. (2010). Chemistry: The central science (11th ed.). McGraw-Hill.
  • Petrucci, R. H., Harwood, W. S., & Herring, F. G. (2011). General chemistry: Principles and modern applications (10th ed.). Pearson Education.