Bond Enthalpies

Some average bond enthalpies, in kJ/mol, are as follows:
H-H = 436
Cl-Cl = 242
H-Cl = 431
What is the enthalpy change for the decomposition of hydrogen chloride?
2 HCl --> H₂ + Cl₂

• -184 kJ
• + 184 kJ
• - 247 kJ
• + 247 kJ

Tags

NGSS.HS-PS1-4

The average bond enthalpies for O-O and O=O are 146kJ/mol and 496kJ/mol respectively. Calculate the enthalpy change for the reaction shown.

• -102kJ

• +102kJ

• +146kJ

• -248 kJ

Tags

NGSS.HS-PS1-4

Calculate the enthalpy change, in kJ/mol for the reaction

H_{2 (g)} + ½O_{2 (g)} → H₂O _(g)

Data of bond energy:

H−H = +436 kJ/mol

O=O = +498 kJ/mol

H−O = +464 kJ/mol

• −243 kJ/mol

• −6 kJ/mol

• +6 kJ/mol

• +221 kJ/mol

Tags

NGSS.HS-PS1-4

The enthalpy change for the reaction between hydrochloric acid and sodium hydroxide is −56 kJ/mol. Therefore ...

• the reaction is exothermic and the temperature rises

• the reaction is exothermic and the temperature falls

• the reaction is endothermic and the temperature rises

• the reaction is endothermic and the temperature falls

Tags

NGSS.HS-PS1-4

Which of these diagram correctly represent an endothermic reaction?

• 
• 
• 
• 

Tags

NGSS.HS-PS1-4

In an endothermic reaction in aqueous solution, which of the following is correct?

• temperature increases, sign of enthalpy change is positive

• temperature increases, sign of enthalpy change is negative

• temperature decreases, sign of enthalpy change is positive

• temperature decreases, sign of enthalpy change is negative

Tags

NGSS.HS-PS1-5

Example of endothermic reaction is ...

• Combustion

• Photosynthesis

• Neutralization

• Respiration

Tags

NGSS.HS-PS1-4

What happens when chemical bonds are broken?

• Energy is released

• An explosion occurs

• An exothermic process take place

• An endothermic process take place

Tags

NGSS.HS-PS1-4