Energy Changes and Chemical Reactions

Water can be used to produce hydrogen gas.

2H₂O → 2H₂ + O₂

Which one of the following that describes bond breaking in the reactant?

• endothermic,

  heat absorbed

• endothermic,

  heat released

• endothermic,

  heat released

• exothermic,

  heat released

Tags

NGSS.HS-PS1-4

The energy level diagram for the reaction between P and Q to form R and S is shown.

Which row describes the energy changes involved and the type of reaction?

• more energy is given out when the bonds in the products

  are formed than is needed to break the bonds in the reactants

  
  

  Type Reaction: endothermic

• more energy is given out when the bonds in the products

  are formed than is needed to break the bonds in the reactants

  
  

  Type Reaction: exothermic

• more energy is needed to break the bonds in the reactants

  than is given out when the bonds in the products are formed.

  
  

  Type Reaction: endothermic

• more energy is needed to break the bonds in the reactants

  than is given out when the bonds in the products are formed.

  
  

  Type of reaction: exothermic

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4

The equation for the reaction is shown.

What is the energy change for the reaction?

• –1420 kJ / mol

• –120 kJ / mol

• +120 kJ / mol

• +1420 kJ / mol

Tags

NGSS.HS-PS1-4

The overall energy change for this reaction is –184 kJ / mol.

What is the energy of the Cl–Cl bond?

• –240 kJ / mol

• –190 kJ / mol

• +190 kJ / mol

• +240 kJ / mol

Tags

NGSS.HS-PS1-4

NGSS.HS-PS1-7

The energy change for this reaction is –95 kJ / mol.

What is the bond energy of the N–N bond?

• 158 kJ / mol

• 315 kJ / mol

• 348 kJ / mol

Tags

NGSS.HS-PS1-4

What is the energy given out during the reaction?

• –3226 kJ / mol

• –884 kJ / mol

• –486 kJ / mol

• –442 kJ / mol

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

Which statement about the reaction is not correct?

• Energy is given out during the reaction.

• The products are at a lower energy level than the reactants.

• The reaction is endothermic.

• The reaction is exothermic.

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4

Which reaction is endothermic?

• acid neutralising alkali causing a temperature increase

• adding magnesium to hydrochloric acid

• calcium carbonate decomposing when heated

• combustion of fossil fuels

Tags

NGSS.HS-PS1-4

Which statements about exothermic and endothermic reactions are correct?

• 1,2,3

• 1 and 2

• 1 and 3

• 2 and 3

Tags

NGSS.HS-PS1-4

The diagram shows that the reaction is ............ .

Increasing the temperature increases the rate of reaction. A reason for this is that the ............. .

• endothermic

  activation energy decreases

• endothermic

  collision rate increases

• exothermic

  activation energy decreases

• exothermic

  collision rate increases

Tags

NGSS.HS-PS1-5