Bonding and Intermolecular Forces Review

Which of the following can be inferred from the diagram above that shows the dependence of potential energy on the internuclear distance between two atoms?

• The atoms form a bond with a bond length of 25pm.

• The atoms form a bond with a bond length of 75pm

  75pm.

• The net force between the atoms is attractive at 25pm

  25pm.

• The net force between the atoms is attractive at 75pm

  75pm.

Answer explanation

The minimum potential energy occurs at an internuclear distance of 75pm, which corresponds to the length of the stable bond that forms between the two atoms. If the atoms were any closer to each other, the net force would be repulsive. Likewise, if the atoms were farther from each other, the net force would be attractive. At 75pm, the net force between the two atoms is zero.

Tags

NGSS.HS-PS3-2

Based on the data in the tables above, which of the following statements provides the best prediction for the boiling point of NaCl ?

• NaCl will have a lower boiling point than NaF because the coulombic attractions are weaker in NaCl than in NaF .

• NaCl will have a boiling point between that of NaF and MgO because the covalent character of the bonds in NaCl is intermediate between that of MgO and NaF.

• NaCl will have a higher boiling point than MgO because the ions are spaced farther apart in NaCl .

• NaCl will have a higher boiling point than MgO because the energy required to transfer electrons from the anion to the cation is larger in NaCl than in MgO .

Answer explanation

The Cl− ion is larger than the F− ion so the attractive interactions in NaCl are weaker than in NaF.

Tags

NGSS.HS-PS1-3

NGSS.HS-PS2-4

Has a central atom with less than an octet of electrons

• H₂O

• NH₃

• BH₃

• CH₄

• SiH₄

Tags

NGSS.HS-PS1-1

Has two lone pairs on the central atom.

• H₂O

• NH₃

• BH₃

• CH₄

• SiH₄

Predicted to have the largest bond angles.

• H₂O

• NH₃

• BH₃

• CH₄

• SiH₄

Has trigonal pyramidal molecular geomtry.

• H₂O

• NH₃

• BH₃

• CH₄

• SiH₄

The potential energy as a function of internuclear distance for three diatomic molecules, X2, Y2, and Z2, is shown in the graph above. Based on the data in the graph, which of the following correctly identifies the diatomic molecules, X2, Y2, and Z2?

• X2 = H₂ , Y2 = N₂ , Z2= O₂

• X2 = N₂ , Y2 = H₂ , Z2= O₂

• X2 = O₂ , Y2 = N₂ , Z2= H₂

• X2 = O₂ , Y2 = H₂ , Z2= N₂

Tags

NGSS.HS-PS1-2

NGSS.HS-PS1-4

The lattice energy of a salt is related to the energy required to separate the ions. For which of the following pairs of ions is the energy that is required to separate the ions largest? (Assume that the distance between the ions in each pair is equal to the sum of the ionic radii.)

• Na+(g) and Cl−(g)

• Cs+(g) and Br−(g)

• Mg2+(g) and O2−(g)

• Ca2+(g) and O2−(g)

Answer explanation

The most tightly bonded ions will be those with the highest oxidation number. Though Mg and Ca both have an oxidation number of 2+ , since Mg is the smaller ion (atom as well), it will have a smaller radius leading to a stronger bond and higher lattice energy.

Tags

NGSS.HS-PS1-3

NGSS.HS-PS2-4

NH₃ reacts with BF₃ to form a single species. Which of the following structural diagrams is the most likely representation of the product of the reaction?

• 
• 
• 
• 

Answer explanation

The lone pair of N can be shared and both N and B will have an octet.

F and H can only form one bond and will not be able to bond twice as shown in the incorrect options.

Tags

NGSS.HS-PS1-3

NGSS.HS-PS1-2

NGSS.HS-PS1-4

The melting point of MgO is higher than that of NaF. Explanations for this observation include which of the following?

I. Mg2+ is more positively charged than Na+.

II. O2- is more negatively charged than F-.

III. The O2- ion is smaller than the F- ion.

• I and II only

• II only

• I and III only

• II and III only

• I, II , and III

Tags

NGSS.HS-PS1-3