I\'m having trouble with these last 3 problems for homework. Can you please expl

Question

I'm having trouble with these last 3 problems for homework. Can you please explain how you got to that answer.

1. Which one of the following substances should exhibit hydrogen bonding in the liquid state? A. PH3 B.H2 C. H2S D. CH4 E. NH3

2. Which of the following properties indicates the presence of strong intermolecular forces in liquid? A. a low heat of vaporization B. a low critical temperature C. a low vapor pressure D. a low boiling point E. none of the above

3. Which one is a covalent network solid? A. SiO2 B. K C. I2 D. CaCl2 E. None of these

Explanation / Answer

1. Which one of the following substances should exhibit hydrogen bonding in the liquid state? A. PH3 B.H2 C. H2S D. CH4 E. NH3

   Answer is E. NH3

We can tell easily by comparing electronegativies of respective elements.

electronegativies means tendency of an atom to attract electrons towards itself.

First compare the electronegativies values

P – 2.19   H – 2.20

H – 2.20 H – 2.20

H- 2.20 S – 2.58

C – 2.55 H – 2.20

N – 3.04 H – 2.20

In NH3 difference of electronegativies between N and H is more so N becomes positive and it can attract H. therefore NH3 exhibits hydrogen bonding in the liquid state.

In remaining cases electronegativies difference is less so they will not form hydrogen bonding in liquid state.

Ans:

Answer: C. a low vapor pressure

Heat of vaporization is enthalpy change required to convert a given substance from liquid to gas. If liquid has strong intermolecular forces then heat of vaporization required more.

Compounds having strong intermolecular forces tend to form a liquid phase over a very large temperature range and so they will have high critical temperatures.

If any compound has strong intermolecular forces in liquid, then you need more energy to transform it from liquid phase to vapour phase, so its boiling point will be higher.

vapor pressure defined as pressure of vapour in contact (or equilibrium) with its liquid or solid. If any compound has strong intermolecular forces in liquid then transformation to vapour state is difficult so vapor pressure will decrese.

3. Which one is a covalent network solid? A. SiO2 B. K C. I2 D. CaCl2 E. None of these

Answer A. SiO2

In covalent network solid atoms are bonded by covalent bonds in a continuous network throughout the material.

Ex: diamond, graphite, SiO2

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.