An exothermic reaction is defined by the release of energy into the surroundings, typically in the form of heat. This results in an increase in the temperature of the surroundings and a decrease in the enthalpy of the chemical system.
472
How is an endothermic reaction defined in terms of heat exchange?
An endothermic reaction is a chemical process that requires an input of energy from its surroundings to proceed. This energy is typically absorbed in the form of heat, resulting in a positive change in enthalpy (ΔH > 0). As the system absorbs thermal energy, the temperature of the immediate surroundings often decreases, distinguishing it from exothermic reactions which release heat into the environment.
473
Which of the following processes are classified as exothermic reactions?
Exothermic reactions are those that release energy to the surroundings, usually as heat. Burning natural gas (combustion) releases significant heat. Cellular respiration is a metabolic process that releases energy stored in glucose. The decomposition of organic matter into compost is a biological oxidation process that also releases heat. Since all these processes involve a net release of energy, they are all correctly identified as exothermic.
474
Which of the following factors leads to an increase in the rate of evaporation?
Evaporation is a surface phenomenon. Increasing the surface area exposes more molecules to the air, allowing a greater number of molecules to escape into the vapor phase simultaneously. Conversely, high humidity, low wind speed, or low temperature would typically decrease the rate of evaporation.
475
What happens to the enthalpy of a substance during the process of liquid evaporation?
Evaporation is an endothermic phase transition where liquid molecules absorb latent heat to overcome intermolecular forces and transition into the gas phase. Because the system absorbs energy from its surroundings to facilitate this change, the total enthalpy of the substance increases during the process.
476
In a vapour compression cycle, which type of tubes are used for Ammonia as a refrigerant?
In the context of using Ammonia as a refrigerant in a vapour compression cycle, it is essential to use steel tubes for the following reasons: 1. Steel is a suitable material for handling corrosive substances like Ammonia. Ammonia can react with copper, causing corrosion and degrading the efficiency of the refrigeration system. 2. Steel tubes provide better thermal conductivity compared to copper, ensuring efficient heat exchange between the refrigerant and the environment. 3. Using steel tubes reduces the risk of tube failure due to Ammonia's corrosive nature, leading to better system reliability and longevity.
477
What study focuses on the energy of a chemical system?
Thermochemistry is a branch of chemistry that deals with the relationship between chemical reactions and energy changes. It involves the measurement and calculation of energy changes in chemical reactions, including heat transfer and thermodynamic properties.
478
Molar heat of vaporization of water is_________________?
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479
Reaction in which heat evolves is called ____________________?
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480
If steel is heated to a temperature well below red heat and is then cooled slowly, the process is called_________?
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