Question

1) Van der Waals forces include both attractive and repulsive components.

Select one:

True False

2) Like Coulombic forces, van der Waals forces show a distance dependence .

Select one:

True False

3) The weakest hydrogen bonds have O-H...O bond angles of 180 degree.

Select one:

True False

4) Which intermolecular force has the longest range?

Select one:

a. monopole-monopole

b. monopole-dipole

c. monopole-induced dipole

d. dipole-induced dipole

e. dipole-dipole

5) Why is it easier to remove 2s electron from Li compared to a 1s electron?

Select one:

a. The 2s electrons feel greater Coulombic repulsion from the nucleus.

b. In part, because the radical extent of the 1s orbital is greater than thatof the 2s orbital.

c. The 1s orbital is higher in energy than the 2s orbital.

d. In part, because the 1s electrons shieldthe 2s electrons from Coulombic attraction to the nucleus.

6. Provide a rationale for why n-octane (linear compound) has a boiling point of 126 degree C whereas branched isomer 2,2,3,3-tetramethylbutane has a melting point of 107 degree C. Your answer should also include a mention of symmetry and point groups.

7) Is the distance dependence for a permanent dipole-permanent dipole interaction always 1/r^3 ? Justify your answer.

8) Match the potential energy distance dependence with the intermolecular force described

Monopole-permanent dipole 1/r^2

induced dipole-induced dipole 1/r

Permanent dipole-permanent dipole (fixed) 1/r^6

Dipole-induced dipole 1/r^3

monopole-monopole 1/r^4

Monopole-induced dipole

Answer 1

Following is the - complete Answer -&- Explanation: for the first four questions ( i.e. Q.1 -to- Q.4 ), of the given: Question Set.....in.....typed format....

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Question - 1:

Answer:

TRUE ----- van der Waals forces include both attractive: and repulsive: components.

Explanation:

As we know the van der Waals forces are a type inter-atomic/ inter-molecular force, which is distance dependent. As long as the distance, between molecules/atoms ,remain greater than the van der Waals radius , the van der Waals force, existing between the atoms / molecules remain: attractive. But, when the distance between the atoms / molecules becomes less than : the van der Waals radius, of the molecules / atoms, the van-der-Waals force existing between the molecules  / atoms, become repulsive force, which can be considered as a repulsive component: Of the van der Waals force(s).

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Question - 2:

Answer:

TRUE ------------- like Coulombic forces, van-der-Waals forces: are also distance dependent forces.

Explanation:

As we have discussed above, as long as the distance between molecules / atoms, remain greater than: the van-der-Waals radius: of the molecules / atoms, the inter-molecular/ inter-atomic, van der Waals force, remain attractive, and whenever, the inter-molecular/ inter-atomic distance, becomes less than: the van der Waals radius: of the atoms/ molecules, the inter-moleculear/ inter-atomic van der Waals force: becomes a repulsive van der Waals force.

Therefore, we can surely say, the van der Waals forces: are distance dependent also/ as well....

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Question - 3:

Answer:

TRUE --------- i.e. the weakest hydrogen bonds, have the O-H......O , bond angles of 180^o .

Explanation:

As we know, the strength of the hydrogen bonds: vary with distance: between the O-H....O atoms. As we know, the distance between the O , and H atoms: will be the largest, when the O-H.....O , bond angle becomes equal to 180^o  , and therefore, the 'O' -and- 'H' atoms: will be the farthest from each other , and therefore will be the weakest.

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Question - 4:

Answer:

Option - ( e ): dipole-dipole

Explanation:

As we know, the dipole-dipole inter-molecular interaction, has the strongest value: and have the longest range: as well.

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