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FREE CHEMISTRY AND STUDY GAMES ABOUT

CHEM.200-10.SHAPES EXAM QUESTIONS

Actual Qs and Ans Expert-Verified Explanation

This Exam contains:

-Guarantee passing score -89 Questions and Answers -format set of multiple-choice -Expert-Verified Explanation

Question 1: Example of a free radical

Answer:

NO2 (nitrogen dioxide); a major contributor to urban smog. It is formed when NO in auto exhaust is oxidized. It has several resonance forms, including two forms with a lone electron delocalized over the N and O.

Question 2: Dipole movement

Answer:

(Greek letter mu) is the product of the partial charges and the distance between them. Measured in debye (dih-bye) units (Coulomb*meter)

Question 3: Small formal charges (positive or negative) are ...

Answer:

Preferable to larger ones

Question 4: Nanotube

Answer:

Younger cousins of fullerenes consist of long, thin, graphite-like cylinders with fullerene ends. They are often nested within one another. They are highly conductive and 40 times stronger than steel despite being so thin.

Question 5: Electron-pair delocalization (AKA simply "delocalization")

Answer:

The process by which electron density is spread over several atoms rather than remaining between two.Note: in metals, electrons are delocalized over the entire sample which is more extensive than in a resonance hybrid

Question 6: How to depict the Lewis structure of a polyatomic ion

Answer:

Bracket the entire structure and write the charge at the top right.Question 7: Benzene: what is the line that runs along within the ring?

Answer:

The line depicts the electron-pair delocalization due to it being a resonance structure Question 8: Exception to octet rule: Odd-Electron molecules

Answer:

A few molecules contain a central atom with an odd number of valence electrons, so they cannot possibly have all their electrons in pairs. Such species, called free radicals, contain a lone (unpaired) electron.

Question 9: Formal charges must sum to...

Answer:

The actual charge on the species: zero for a molecule and the ionic charge for an ion.

Question 10: Tetrahedral arrangement

Answer:

The geometric arrangement formed when four electron groups maximize their separation around a central atom; when all four groups are bonding groups, the molecular shape is a tetrahedral.

Question 11: Shape of ethane

Answer:

CH3CH3 (molecular formula: C2H6) with four bonding groups and no lone pairs around each of the two central carbons, ethane is shaped like two overlapping tetrahedra.

Question 12: Linear electron-group arrangement's class

Answer:

Class = AX2, e.g. beryllium chloride: BeCl2 and carbon dioxide: CO2

Question 13: Is the formal charge the same as the oxidation number?

Answer:

No

Question 14: Linear arrangement

Answer:

The geometric arrangement obtained when two electron groups maximize their separation around a central atom.

Question 15: 4 steps in converting a molecular formula into a Lewis structure

Answer:

(1) Place atom with lowest EN in center. (2) Add A-group numbers. (3) Draw single bonds. Subtract 2e- for each bond. (4) Give each atom 8e- (2e- for H).

Question 16: Formal charge

Answer:

The charge an atom would have if the bonding electrons were shared equally. An atom's formal charge is its total number of valence electrons minus all of its unshared valence electrons and half of its shared valence electrons.

Question 17: Bond angle in a trigonal pyramid

Answer:

Stronger repulsions due to the lone pair make the measured bond angle slightly less than the ideal 109.5

Question 18: Why are free radicals dangerous?

Answer:

The delocalized electron reacts with H atoms contained in biomolecules, forming covalent bonds with them. The biomolecule now has a lone electron and is itself a free radical which will disrupt other biomolecules

Question 19: Does water have a dipole movement?

Answer:

Yes, the bond polarities are not counterbalances because water has a V shape. The O end is more negative than the H end.Question 20: To construct the molecular shape from the Lewis structure, chemists employ...

Answer:

Valence-shell electron-pair repulsion (VSEPR) theory

Question 21: Ideal bond angles

Answer:

Bond angles predicted by simple geometry alone. They are observed when all the bonding electron groups around a central atom are identical and are connected to atoms of the same element.Question 22: Which position within the trigonal bipyramidal arrangement do lone pairs exist?

Answer:

Since lone pairs exert stronger repulsions than bonding pairs, lone pairs occupy equatorial positions.Question 23: For similar molecules within a given electron-group arrangement, electron-pair

repulsions cause deviations from ideal bond angles in the following order:

Answer:

Lone pair-lone pair > lone pair-bonding pair > bonding pair-bonding pair Question 24: Most important molecule with bent tetrahedral shape. Bond angle? Compare bond angle with the trigonal pyramidal tetrahedral NH3 molecule's bond angle. Then compare both to ideal bond angle of a tetrahedral shaped molecule.

Answer:

Water. Bond angle between bonding (O-H) groups is 104.5 degrees. NH3's is 107.3 degrees between bonding groups. Ideal is 109.5 degrees. Thus there is an order, which is described on next card.

Question 25: Molecular polarity

Answer:

Molecules with net imbalances of charge have a molecular polarity.