(1) Gas-phase molecules are free to moveabout their container. In liquids and so

Question

(1) Gas-phase molecules are free to moveabout their container. In liquids and solids, molecules areheld closely together by the intermolecular forcesdescribed in section 11.2 of your Chang textbook. Which of the following substances exhibit(s) the intermolecularforces known as hydrogen bonding? (Assume thesesubstances are in the liquid or solid phase.)

                       N2              H2             H2O            CH4      

(2) Which of the following substancesexhibit(s) the intermolecular interactions known as dispersionforces? (Assume these substances are in the liquid orsolid phase.)

                       N2              H2             H2O            CH4      

(3) During sublimation, molecules escapefrom the surface of a solid and enter the gas phase. This isa physical change; each molecule simply breaks free of theintermolecular interactions it shares with neighboringmolecules. Is sublimation an exothermic or endothermicprocess?

(4) Run room-temperature water over yourhands and wave them in the air to dry. Record yourobservations. Propose possible explanations for yourobservations.

(5) Hold a small piece of ordinary ice inyour hand and allow it to melt completely. Record yourobservations and propose possibleexplanations.

Explanation / Answer

   1) Hydrogen bonding : The Hydrogen bond is aspecial type of dipole -dipole interaction between the hydrogenatom in a polar bond ,Such as N-H ,O-H ,F-H and an electronegativeO, N ,or F atom .      From the given compounds  H2O only forms Hydrogen bonds .     2) dispersionforces  ,attractive forces thet arise as a result oftemperory dipoles induced in atoms or molecules .At very lowtemperatures  dispersion forcesare strong enough to holdHe atom together .          dispersionforces usually increase with molar mass because molecules withlarger mass tend to have more electrons ,And   dispersion forces  in creasesstrength with number of electrons .         From the givencomponds molar mass of the H2 O is havinglarger molar mass 18 g/mol.         So this is havingHigher dispersion forces 3) Sublimation is the transition of a solid [S] to avapor [V]. In the direction as written above: [S] ---> [V],[L] --->
[V], and [S] ---> [L] all the transitions require the absorptionof heat
and so are endothermic. 4) Run room-temperature water over our hands and wave them in the air to dry.then initially someamount of water is Evaporated due to gain some heat from our hand.When our hand is Shaken for wave nature of water then theEquilibrium is destrubed between the water vapor and water .Thensome Amount of water again try to vaporised .Due to this situationWe vaporise the more amount of water . 5) a small piece of ordinary ice in our handand allow it to melt completely.Because of it takes heat from ourhands to Evoparrate .This is also Endothermic reaction .

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