Spontaneous and nonspontaneous reactions

What is a spontaneous process in chemistry?

• A process that requires external intervention process that requires external intervention

• A process that occurs without outside intervention

• A process that always absorbs energy

• A process that is always exothermic

Which of the following is an example of a spontaneous process?

• Boiling water in a kettle

• Charging a battery

• Rusting of iron

• Mixing sugar in water

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NGSS.HS-PS3-4

Some spontaneous processes (combustion reactions) require what type of energy from the surroundings?

• Electrical energy
  

• Thermal energy

• Kinetic energy

• Magnetic energy

In the chemical equation 2Fe2O3 (s) → 4Fe (s) + 3O2 (g) AH=+1625 kJ , what is the change in enthalpy (ΔH) for the reverse form of this reaction?

• a) -1625 kJ

• b) +1625 kJ

• c) 0 kJ

• d) -325 kJ

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NGSS.HS-PS1-4

What happens to the sign of ΔH when you reverse the direction of a chemical reaction?

• a) It stays the same

• b) Changes to the opposite sign

• c) It becomes positive

• d) It becomes zero

Is the formation of rust on iron an exothermic or endothermic reaction?

• a) Exothermic

• b) Endothermic

Tags

NGSS.HS-PS1-4

Which of the following reactions is both spontaneous and exothermic?

• a) Photosynthesis

• b) Combustion of gasoline

• c) Melting ice

• d) Dissolving salt in water

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NGSS.HS-PS1-4

What factor primarily determines the spontaneity of a chemical reaction?

• a) Temperature

• b) Pressure

• c) ΔH (enthalpy change)

• d) Concentration of reactants

Which process requires an external energy source to proceed?

• a) Freezing water

• b) Boiling water

• c) Condensing water vapor

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NGSS.MS-PS1-4

NGSS.MS-PS3-4

How can the knowledge of spontaneity and energy changes in chemistry be applied in everyday life (e.g.: Iron rusting)?

• a) By making coffee

• b) By predicting weather patterns

• c) By controlling chemical reactions for various purposes

• d) By charging a smartphone

Tags

NGSS.HS-PS1-4