Understanding Enthalpy and Gibbs Energy

What is the enthalpy of formation for a compound?

• The energy required to break a chemical bond

• The change in enthalpy when one mole of a compound is formed from its elements in their standard states

• The energy released during a phase change

• The change in entropy during a chemical reaction

Which of the following best describes entropy changes in reactions?

• Entropy always decreases in a chemical reaction

• Entropy is the measure of disorder or randomness in a system

• Entropy is the energy required to start a reaction

• Entropy is the heat content of a system

What is the Gibbs free energy equation?

During a phase change, what happens to the enthalpy of a substance?

• It remains constant

• It decreases

• It increases

• It can either increase or decrease depending on the phase change

How do you calculate standard entropy change for a reaction?

• By subtracting the sum of the standard entropies of the reactants from the sum of the standard entropies of the products

• By adding the standard entropies of the reactants and products

• By dividing the standard entropies of the products by the reactants

• By multiplying the standard entropies of the reactants and products

Which of the following conditions indicates a spontaneous reaction in terms of Gibbs free energy?

• The reaction is non-spontaneous

• The reaction is at equilibrium

• The reaction is spontaneous

• The reaction absorbs energy

Which of the following statements is true about the enthalpy of formation for elements in their standard state?

• It is always positive

• It is always negative

• It is zero

• It varies depending on the element

In which scenario would the entropy of a system likely increase?

• When a gas condenses into a liquid

• When a solid melts into a liquid

• When a liquid freezes into a solid

• When a gas is compressed into a liquid

• The system has become more ordered

• The system has become more disordered

• The system has lost energy

• The system is at equilibrium

Tags

NGSS.HS-PS3-4