1. Using principles of chemical bongingand molecular geometry, explain each of t
ID: 689911 • Letter: 1
Question
1. Using principles of chemical bongingand molecular geometry, explain each of the followingobservations. Lewis electron-dot diagrams and sketches ofmolecules may be helpful as part of your explanations. Foreach observation, your answer must include references to bothsubstances.a. the bonds in nitrite ion, NO2- , are shorter than the bonds in nitrateion, NO3 -
b. TheCH2F2molecule is polar, whereas theCF4 molecule is not.
c. The atoms in a C2H4molecule are located in a single plane, whereas those in aC2H6 molecule are not.
d. The shape of a PF5 moleculediffers from that on an IF5 molecule
e. HClO3 is stronger acid thanHClO
Explanation / Answer
a. the bonds in nitrite ion, NO2- , are shorter than the bonds in nitrateion, NO3 -Because both anions havenegative charges, they have resonance structures...the nitrate ion(NO3-) has more negative charge and these extra electrons repel thenucleus making the bonds longer than those of the nirtite ion.
b. The CH2F2molecule is polar, whereas theCF4 molecule is not.
The CF4 molecule has tetrahedral geometry, meaning that each F atomis at the points of a "triangular pyramid" with the C atom at thecenter-this results in polar bonds becuase Fluorine is the mostelectronegative, but all the bonds pull from opposite directionsand cancel each other out. The CH2F2 molecule can be polar becauseit depends on which way you draw the Lewis Structure. When the Fatoms are drawn on the same side of the C=C double bond, the atomis polar, when they are drawn on opposite sides, it is nonpolar.
c. The atoms in a C2H4 molecule are locatedin a single plane, whereas those in a C2H6molecule are not.
The C2H4 molecule has a C=C double bond, this results in themolecule not being able to rotate about the C-C because the C's areheld together by sigma bonds and also pi bonds. The C2H6 moleculehas a C-C single bond and is only connected by sigma bonds whichallow rotation.
d. The shape of a PF5 molecule differs from that on anIF5 molecule. The phosphorous pentafluoride (PF5) does nothave any lone pair electrons to change its geometry which istrigonal bipyramidal=3 equatorial F atoms at the points oftriangle, and 2 linear F atoms that are above and below theequatorial ones. The iodine pentafluoride (IF5) has a lone pair onthe Iodine which causes the F atoms to bend toward each other.Think of the Iodine atom as the center of a square with fourFluorines at the corners of the square and the fifth fluorine atthe point of a pyramid directly above the Iodine. The lone pairsare directly below the iodine.
e. HClO3 is stronger acid than HClO
The HClO3 is stronger because it can more easily donate its H+. The3 oxygens are highlly electronegative makine the entire moleculevery polar. The oxygens pull the electrons away from the H-CL bondso the H can be cleaved off much easier than in the HClOmolecule.
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