Exam 3 bys

What is Gibbs Free Energy, and why is it important?

• It measures the temperature of a reaction.

• It indicates the spontaneity of a reaction.

• It calculates the pressure of a system.

• It determines the color change in a reaction.

Answer explanation

Gibbs Free Energy indicates the spontaneity of a reaction by determining whether a process can occur without external energy. A negative Gibbs Free Energy value suggests that the reaction is spontaneous.

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NGSS.HS-PS1-4

NGSS.HS-PS3-1

What is the formula for calculating ΔG?

• ΔG = ΔH + TΔS

• ΔG = ΔH - TΔS

• ΔG = ΔH / TΔS

• ΔG = ΔH * TΔS

Answer explanation

The correct formula for calculating Gibbs free energy (ΔG) is ΔG = ΔH - TΔS. Here, ΔH represents the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy.

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NGSS.HS-PS3-1

How can we predict the spontaneity of a reaction?

• By measuring the color change.

• By checking the pH level.

• By comparing enthalpy and entropy changes.

• By observing the physical state.

Answer explanation

The spontaneity of a reaction can be predicted by comparing enthalpy and entropy changes using the Gibbs free energy equation. This approach considers both energy and disorder, unlike the other options which do not directly indicate spontaneity.

What are the two types of reactions based on ΔG?

• Endothermic and Exothermic

• Catalytic and Non-catalytic

• Endergonic and Exergonic

• Oxidative and Reductive

Answer explanation

The two types of reactions based on ΔG are endergonic and exergonic. Endergonic reactions absorb energy (positive ΔG), while exergonic reactions release energy (negative ΔG). This distinction is crucial in thermodynamics.

What is activation energy?

• The energy released during a reaction.

• The energy required to start a reaction.

• The energy absorbed by the products.

• The energy lost as heat.

Answer explanation

Activation energy is the minimum energy required to initiate a chemical reaction. It is essential for breaking bonds in reactants, allowing the reaction to proceed, making 'The energy required to start a reaction' the correct choice.

How can the rate of a reaction be increased?

• Decreasing the temperature.

• Decreasing the concentration of reactants.

• Increasing the temperature and concentration of reactants.

• Increasing the pressure only.

Answer explanation

The rate of a reaction can be increased by raising the temperature, which provides more energy to the reactants, and by increasing their concentration, which leads to more frequent collisions. Thus, the correct choice is increasing both.

Tags

NGSS.HS-PS1-5

What are the properties of ATP, and why is it important?

• ATP is a protein that stores genetic information.

• ATP is a lipid that forms cell membranes.

• ATP is a nucleotide consisting of adenine, ribose, and three phosphate groups.

• ATP is a carbohydrate used for structural support.

Answer explanation

ATP, or adenosine triphosphate, is a nucleotide made of adenine, ribose, and three phosphate groups. It is crucial for energy transfer in cells, powering various biological processes.

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How do enzymes function as macromolecules?

• Enzymes are lipids that store energy.

• Enzymes are proteins that speed up reactions without being consumed.

• Enzymes are carbohydrates that provide structural support.

• Enzymes are nucleic acids that store genetic information.

Answer explanation

Enzymes are specialized proteins that act as catalysts, accelerating chemical reactions in biological systems without being consumed in the process. This distinguishes them from lipids, carbohydrates, and nucleic acids.

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NGSS.HS-LS2-3

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What is the difference between active and allosteric sites?

• The active site is where molecules bind to regulate enzyme activity.

• The active site is where substrates bind, while the allosteric site regulates enzyme activity.

• The allosteric site is where substrates bind, while the active site regulates enzyme activity.

• Both sites are identical and serve the same function.

Answer explanation

The correct choice states that the active site is where substrates bind, while the allosteric site regulates enzyme activity. This distinction is crucial for understanding enzyme function and regulation.

What is feedback inhibition?

• A process where enzymes are permanently deactivated.

• A mechanism where the end product of a pathway inhibits an earlier step.

• A method of increasing enzyme production.

• A way to enhance substrate binding.

Answer explanation

Feedback inhibition is a regulatory mechanism where the end product of a metabolic pathway inhibits an earlier step, preventing overproduction and maintaining balance in the cell's metabolic processes.

Tags

NGSS.HS-LS1-3