Spontaneous Reactions

What does Gibbs Free Energy tell us?

• How much energy is given off by a reaction.

• The tendency of a reaction to become "random"

• How spontaneous a reaction is.

What information do we need to perform a calculation of Gibbs Free Energy?

• Enthalpy of the reaction.

• Entropy of the reaction.

• The temperature of the reaction in Kelvin.

• All of the above are needed.

Spontaneous reactions may be extremely slow.

• True
• False

Tags

NGSS.HS-PS1-5

Which of the following would most likely lead to a spontaneous reaction.

• A high negative enthalpy.

• A low negative enthalpy.

• A high positive enthalpy.

• A low positive enthalpy.

Tags

NGSS.HS-PS1-4

A reaction has a positive ΔH and a positive ΔS. Which of the following is true?

• It will be spontaneous at all temperatures.
• It will be nonspontaneous at all temperatures.
• It will be spontaneous at low temperatures.
• It will be spontaneous at high temperatures.

Your enthalpy is high and negative but your entropy is also negative. What type of temperature would you want to get a spontaneous reaction?

• low

• high

Your enthalpy is positive and your entropy is positive. What type of temperature would you want to ensure a spontaneous reaction.

• very high

• very low

Which combination of ΔH and ΔS NEVER has a spontaneous reaction?

• +ΔH and +ΔS

• +ΔH and -ΔS

• -ΔH and -ΔS

• -ΔH and +ΔS

For the process at 25⁰C : I₂(g) →I₂(s). What are the signs for ΔG, ΔH and ΔS?

• ΔG + ΔH - ΔS -

• ΔG - ΔH - ΔS -

• ΔG - ΔH + ΔS +

• ΔG - ΔH + ΔS +

Predict the signs of ΔH , ΔS and ΔG for the reaction:

Mg(s) --> Mg(g)

• Δ H = - , Δ S = + and Δ G = - (all temperature)

• Δ H = + , Δ S = + and Δ G = - (At all temperature)

• Δ H = + , Δ S = + and Δ G = - (At low temperature)

• Δ H = + , Δ S = + and Δ G = - (At high temperature)

Tags

NGSS.HS-PS1-4