Entropy and Enthalpy

Given the balanced equation: I₂(s) + energy → I₂(g)

As a sample of I₂(s) sublimes to I₂(g), the entropy of the sample

• 1. increases because the particles are less randomly arranged

• 2. increases because the particles are more randomly arranged

• 3. decreases because the particles are less randomly arranged

• 4. decreases because the particles are more randomly arranged

Which of these changes produces the greatest increase in entropy?

• 1. CaCO₃(s) → CaO(s) + CO₂(g)

• 2. 2 Mg(s) + O₂(g) → 2 MgO(s)

• 3. H₂O(g) → H₂O(l)

• 4. CO₂(g) → CO₂(s)

A thermometer is in a beaker of water. Which statement best explains why the thermometer reading initially increases when LiBr(s) is dissolved in the water?

• The entropy of the LiBr(aq) is greater than the entropy of the water.

• The entropy of the LiBr(aq) is less than the entropy of the water.

• The dissolving of the LiBr(s) in water is an endothermic process.

• The dissolving of the LiBr(s) in water is an exothermic process.

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4

Which one of the following is NOT a key concept of the collision theory:

• particles must collide in order to react

• particles must move slowly when they collide, otherwise they simply “bounce off” one another

• particles must collide with the proper orientation

• particles must collide with sufficient energy to reach the activated complex in order to react

Tags

NGSS.HS-PS2-3

Which one of the following factors does not affect the rate of a chemical reaction:

• humidity

• temperature

• concentration

Tags

NGSS.HS-PS1-5

The rate of a chemical reaction normally

• increases as temperature decreases

• decreases when a catalyst is added

• increases as reactant concentration increases

• decreases as reactant concentration increases

Tags

NGSS.HS-PS1-5

• This reaction is reversible because a gas is generated and the reaction produced an increase in temperature

• This reaction is spontaneous because a gas is generated and the reaction produced an increase in temperature

• This reaction will not occur in real life because because a gas is generated and the reaction produced an increase in temperature.

Tags

NGSS.HS-PS1-4

NGSS.HS-PS1-5

NGSS.HS-PS3-4

Which statement is true regarding this chemical equation:

CH₄(g) + 2O₂(g) --> CO₂(g) + 2H₂O(g)

• One gram of methane is required to react with 2 grams of oxygen gas

• One gram of methane is required to react with 4 grams of oxygen gas.

• One mole of methane is required to react with 4 moles of oxygen gas.

• One mole of methane is required to react with 2 moles of oxygen gas.

Tags

NGSS.HS-PS1-7

When the chemical equation below is balanced, what will be the coefficient for NH₃ ?

NH₃(g) + O₂(g) --> N₂(g) + H₂O(g)

• 4

• 3

• 2

• 6

Tags

NGSS.HS-PS1-7

Given the potential energy diagram for a chemical reaction:Which statement correctly describes the energy changes that occur in the forward reaction?

• The activation energy is 10. kJ and the reaction is

  endothermic.

• The activation energy is 10. kJ and the reaction is

  exothermic.

• The activation energy is 50. kJ and the reaction is

  endothermic.

• The activation energy is 50. kJ and the reaction is

  exothermic.

Tags

NGSS.HS-PS1-4