Self Assessment 08c_Bond Enthalpies

The reaction represented goes essentially to completion. The reaction takes place in a rigid, insulated vessel that is initially at 600 K

Which of the following statements about the bonds in the reactants and products is most accurate?

• The sum of the bond enthalpies of the bonds in the reactant is greater than the sum of the bond enthalpies of the bonds in the products.

• The sum of the bond enthalpies of the bonds in the reactant is less than the sum of the bond enthalpies of the bonds in the products.

• The length of the bond between carbon and oxygen in CH₃OH is shorter than the length of the bond between carbon and oxygen in CO.

• All of the bonds in the reactant and products are polar.

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

• The bond dissociation energy between O atoms in O2 is greater than the sum of the bond dissociation energies of the two O−H bonds in H2O.

• More bonds are formed in the products than are broken in the reactants.

• The sum of the bond dissociation energies of the product molecules is EQUAL to the sum of the bond dissociation energies of the reactant molecules.

• The sum of the bond dissociation energies of the product molecules is GREATER than the sum of the bond dissociation energies of the reactant molecules.

Tags

NGSS.HS-PS1-4

Shown above are the equation representing the decomposition of H2O2(l) and a table of bond enthalpies. On the basis of the information, which of the following is the enthalpy of decomposition of 2 mol of H2O2(l) ?

• −349kJ

• −203kJ

• 203kJ

• 349kJ

Tags

NGSS.HS-PS1-4

A mixture of NO₂(g) and N₂O₄(g) is placed in a glass tube and allowed to reach equilibrium at 70°C, as represented above.

Which of the following statements about ∆H° for the reaction is correct?

• ΔH° < 0 because energy is released when the N−N bond breaks.

• ΔH° < 0 because energy is required to break the N−N bond.

• ΔH° > 0 because energy is released when the N−N bond breaks.

• ΔH° > 0 because energy is required to break the N−N bond.

Tags

NGSS.HS-PS1-4

_____ Hydrogen-Hydrogen single bond/s are broken and _____ Carbon-Hydrogen single bond/s formed

• 6; 8

• 2; 8

• 2; 10

• 6; 10

Tags

NGSS.HS-PS1-2

_____ Carbon-Carbon single bond/s are formed

• 6

• 2

• 3

• 10

Bond enthalpy is the amount of energy is takes to break __________ of a bond.

• one mole

• one gram

• the activation energy

• the binding energy

Tags

NGSS.HS-PS1-4

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

Breaking bonds is _________________. Forming bonds is ______________________

• endothermic, exothermic

• exothermic, endothermic

Tags

NGSS.HS-PS1-4