A few questions

[denticle]

I did the OAT to get some more practice in but don't know how to do these questions. Help pls? I especially don't know how to get answer to the second question.

1. For the reaction between A and B to form C it is found that when one combines 0.6 moles of A with 0.6 moles of B, all of the B reacts, 0.2 moles of A remain UNREACTED and 0.4 moles of C are produced. What is the balanced equation for this reaction?
A. A+2B--> C
B. A+3B--> 2C
C. 3A+3B-->2C
D. 3A+2B-->3C
E. 2A+3B--> 2C (Answer)


2. The bond length in Cl2 is 1.99 Å. The distance separating two adjacent carbon nuclei in diamond is 1.54 Å. Based on these data, what is the length of the C-Cl bond in the compound CCl4?
A. 3.53
B. 2.53
C. 2.16
D. 1.76 (answer)
E. 1.54

3. What is the hybridization of a nitrogen atom if it forms two σ two π bonds?
A. sp
B. sp2
C. sp3 (Answer)
D. sp3d2

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[ktran17]

1. Use molecule B as the limiting reagent and perform mole ratio on both molecule A and C to find out which one will have give you 0.4 reacted A and 0.4 produced C.

2. A bond length usually has columbic attraction and repulsion, but for this problem lets just assume the length of a bond starts from the outer edge of an atom to the other outer edge of an atom. Therefore, take the Cl-Cl bond and divide it by 2 to give you Cl-. similarly, take the C-C bond from the diamond and divide it by 2 to give you C-. These are kinda like half bonds and not charges! Lastly, sum the Cl- and C- bond lengths and you should get an answer around 1.7.

3. I think this question is written wrong.

 

[Toasted]

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[TheDentist16]

For question 3, the nitrogen atom will form a total of four bonds. Using what I like to call the "bond number" trick, you can find the hybridization of the atom by adding the exponents of the answer choices to figure out what the answer is. Since we know that the bond number will be 4 (2 sigma and 2 pi), the exponents of the answer must also add up to four.

The sp3 hybridization can be thought of as s^1p^3, and 1+3 = 4. In a similar manner, we can check the other answers and rule them out. The sp hybridization will be a bond number of 2, sp2 will be 3, and sp3d2 will be s^1p^3d^2, where 1+3+2 = a bond number of 6.

 

[denticle]

Thanks guys!

Thats a really good tip for question 3. I thought it was sp assuming that the N had a single and a triple bond (2s and a 1p for the triple and 1s for the single). I had always associated triple bonds with sp hybridization... :\ guess i was way off. lol