AP Chemistry Entropy Calculations

What phase change brings an increase in entropy?

• g->s
• l->s
• l->g
• g->l

Which interval represents the heat of reaction for the reaction?

• A
• B
• D
• E

Tags

NGSS.HS-PS1-4

As NaCl dissolves according to the equation
NaCl(s) → Na+(aq) + Cl-(aq), the entropy of the system 

• Increases
• Decreases
• Remains the same

Spontaneous reactions are driven by

• increasing enthalpy and increasing entropy.
• decreasing enthalpy and decreasing entropy.
• increasing enthalpy and decreasing entropy.
• decreasing enthalpy and increasing entropy.

Solid magnesium dissolves in a hydrochloric acid, releasing hydrogen gas and heat from a solution of magnesium chloride. What is the sign on ΔH for this reaction?

• Negative because it is exothermic
• Negative because it is endothermic
• Positive because it is exothermic
• Positive because it is endothermic

Tags

NGSS.HS-PS1-4

When ammonium nitrate dissolves in water, the solution gets cold. Which is true?

• Reaction is ENDOTHERMIC with positive ΔH
• Reaction is ENDOTHERMIC with -ΔH
• Reaction is EXOTHERMIC with a -ΔH
• Reaction is EXOTHERMIC with +ΔH

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4

Which one of these would result in a decrease in entropy?

• A solid solute dissolves in water.
• A gas is released.
• A liquid freezes.
• A liquid boils.

Solid magnesium dissolves in a hydrochloric acid, releasing hydrogen gas and heat from a solution of magnesium chloride. What is the sign on ΔS for this reaction?

• Negative because it is becoming more ordered.
• Negative because it is becoming more disordered.
• Positive because it is becoming more ordered.
• Positive because it is becoming more disordered.

Solid magnesium dissolves in a hydrochloric acid, releasing hydrogen gas and heat from a solution of magnesium chloride. What is the sign on ΔG for this reaction?

• Negative because it is spontaneous
• Negative because it is nonspontaneous
• Positive because it is spontaneous
• Positive because it is nonspontaneous

Tags

NGSS.HS-PS1-4

The reaction
A + 2 B₂ + C --> CAB₄
has an enthalpy change of -104 kJ and a change in entropy of -60.8 J/K at 30 °C. What is the free energy and spontaneity of the reaction?  

• -85.6 kJ, spontaneous
• -18.3 kJ, not spontaneous
• +18.3 kJ, spontaneous 
• +85.6 kJ, not spontaneous 

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1