bonding & significant figures

2013-02-21 3:24 pm

1. The reason ammonia is considered to have a dipole-dipole attraction is because
(a) each bond is a dipole
(b) the electrons in all the bonds cloud are displaced towards the nitrogen atom
(c) ammonia exists as several resonance structures that gives rise to dipole-dipole attractions
(d) a and c

the answer is (b)

Why is (a) incorrect? Why is (b) correct?

Are there any examples which exist as several resonance structures that gives rise to dipole-dipole attractions?

2. Why are London forces most pronounced at low temperature and high pressure?

3. [16.050(10^3)] / [(24.8-19.4)(1.057)(453.6)]
(10^3 is exact, while all the other numbers are not exact. )

Why is the answer cor. to 3 s. f., but not 2 s. f.?
(24.8-19.4 = 5.4, which has 2 s. f. )

回答 (1)

Pun

2013-02-27 7:15 pm

✔ 最佳答案

1. We say a molecule has dipole, but not the bond is dipole.
(b) may be a better description than (a). so, (b)

2. Because London forces becomes significant when molecules are close to one another. So, low temperature and/or high pressure.

3. view this
16.050(10^3) / (24.8x1.057 -19.4x1.057 ) x 453.6
Now, would you say 2 sig fig or 3 sig fig?
I believe you will say 3 now.

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