Unit 05, Part I Exam

A reaction between two different gases is most likely to occur when the colliding molecules have the proper orientation and sufficient

• charge

• energy

• mass

• volume

Chemical reactions are most likely to occur when reacting particles collide with the

• proper energy and proper orientation

• proper first ionization energy and proper molecular symmetry

• same mass and the same number of electrons

• same number of valence electrons and the same number of electron shells

A person with a body temperature of 37°C holds a cup of hot water in their hand. The temperature of the cup is 44°C. The air temperature is 22°C. Which phrase describes a heat transfer that occurs in this system?

• from the air to the cup

• from the hand to the cup

• from the air to the hand

• from the cup to the hand

Which statement describes the energy transfer that occurs when a sample of copper at 100.°C is placed in a sample of water at 20.°C?

• Thermal energy is transferred from the copper to the water.

• Thermal energy is transferred from the water to the copper.

• Chemical energy is transferred from the copper to the water.

• Chemical energy is transferred from the water to the copper.

Which statement best describes a chemical reaction in which energy is released?

• It is exothermic and has a negative H.

•  It is exothermic and has a positive H.

• It is endothermic and has a negative H.

• It is endothermic and has a positive H.

The melting of an ice cube is an example of an

• endothermic, chemical change

• endothermic, physical change

• exothermic, chemical change

• exothermic, physical change

Which term represents the disorder of a system?

• entropy

• mole

• quanta

• pressure

Which phase change represents an increase in entropy?

• liquid to gas

• liquid to solid

• gas to solid

• gas to liquid

Systems in nature tend to undergo changes toward

• higher energy and higher entropy

• higher energy and lower entropy

• lower energy and higher entropy

• lower energy and lower entropy

Given the equation representing a phase change for carbon dioxide, CO₂ (s):

CO₂ (s) + energy → CO₂ (g)

Which statement describes this phase change in terms of energy and entropy?

• The phase change is endothermic and entropy increases.

• The phase change is endothermic and entropy decreases.

• The phase change is exothermic and entropy increases.

• The phase change is exothermic and entropy decreases.