Multiple Choice
What is the energy lost when 11.3 g of gold cools from 224 °C to 117 °C, given that the specific heat capacity of gold is 0.129 J/g°C?
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8. Thermochemistry
Endothermic & Exothermic Reactions
Multiple Choice
Which of the following best describes how energy is used in chemical reactions?
A
Energy is only released during the formation of chemical bonds.
B
Energy is absorbed during the formation of chemical bonds.
C
Energy is absorbed to break bonds and released when new bonds are formed.
D
Energy is neither absorbed nor released during chemical reactions.
Verified step by step guidance1
Understand that chemical reactions involve breaking and forming chemical bonds. Energy is required to break bonds, and energy is released when new bonds are formed.
Recognize that the process of breaking bonds is endothermic, meaning it absorbs energy. This is because energy is needed to overcome the forces holding the atoms together.
Identify that the process of forming new bonds is exothermic, meaning it releases energy. This occurs because the system releases energy as atoms come together to form stable bonds.
Consider the overall energy change in a chemical reaction, which is determined by the balance between the energy absorbed to break bonds and the energy released when new bonds are formed.
Conclude that the correct description of energy use in chemical reactions is: 'Energy is absorbed to break bonds and released when new bonds are formed.' This reflects the dynamic nature of energy changes during chemical reactions.
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