Hey guys! Stuck on some review problems: (My maybe answers are at the end)

1)Which of the following molecules has a nonzero dipole moment?
A. CO2 B. H2 C. C12 D. CH4 E. BF3
F. None of the above has a nonzero dipole moment
2) Which of the following would you predict to have the most ionic bond?
A. BeC12 D. BeF2
B. HgC12 E. CsF
C. LiC1 F. MgO
3)The structural unit −CO2H indicates
A. hydrocarbon D. ketone
B. alcohol E. carboxylic acid
C. aldehyde F. amine
4)When NaC1 is dissolved in H2O, the most important intermolecular forces that come into play are:
A. dipole-dipole D. ion-dipole
B. induced dipole-induced dipole E. ion-induced dipole
C. dipole-induced dipole F. None of the above
5)At what temperature can ice, water (liquid) and water vapor all coexist in equilibrium?
A. 0 °C D. −10 °C
B. 78 °C E. 0.01 °C
C. 100 °C F. None of the above
6)A mixture contains 1.00 moles N2, 4.00 moles of O2, 1.00 moles of Ar and 4.00 moles of Xe. What is the mole fraction of Xe in the mixture?
A. 1.000 D. 0.400
B. 0.800 E. 0.200
C. 0.600 F. None of the above
7) When 5.63 g of CdBr2 are added to 100.0 g of H2O, the observed freezing point is −0.54 °C. Kf for H2O = 1.86 °C/molal. Which of the following is most reasonable?
A. CdBr2 is insoluble in H2O
B. CdBr2 is completely dissociated in H2O
C. CdBr2 is moderately dissociated in H2O
D. CdBr2 is just barely dissociated in H2O
E. CdBr2 is a nonelectrolyte
8) To prepare an aqueous 0.1000 molal solution of NaC1, how many g of NaC1 must be added to 500.0 g of H2O?
A. 58.44 g D. 5.844 g
B. 29.22 g E. 0.100 g
C. 2.922 g F. None of the above
Maybe Answers:
1) F
2)E
3)E
4)D
5)E
6)D
7)D
8) C
Thanks! I worked really hard, I'm just unsure!

You would really make it much simpler to check these answers if you had placed the answers with the question instead of at the bottom. It takes oodles of time to scroll up and down looking for the answer and back to the top for another question.

#1 is not right.

I'm so sorry! I didn't even think of that, but I will do that next time! I don't understand number 1, does BF3 have a zero dipole moment? Do the others look okay? Thanks so much!!!

2 is right.

Yes, the answer to 1 is BF3.

3 is right.

4 is right.

5 is right.

5 is right.

https://en.wikipedia.org/wiki/Triple_point

6 is right.

I don't agree with 7.

I suggest you calculate delta T for the van't Hoff factor of 1, 2, and 3 and compare those values with the 0.54 of the problem. I think you can draw conclusions from that.

8 is OK.

For 7, this my thinking:

Molality of solution:
5.63 g CdBr2 / 272.2 g/mol = 0.0207 mol / 0.1 kg water = 0.207 m
0.54C = i (1.86) (0.207)
i = 1.4
If CdBr2 was completely dissociated, i would be 3. If it was a non-electrolyte, i would = 1. So I guess that's why I think it is barely dissociated. I am super confused. Could you explain it a little then? I'm sorry

I tried the same thing you did and I got confused too. Look at it this way.

If i = 1, then
dT = 1*1.86*0.207 = 0.38

For i = 2, then
2*1.86*0.207 = about 0.77

For i = 3 (complete dissociation) then
3*1.86*0.207 = 1.15

So it is dissociate about half way between i = 1 (no dissociation) and 2(partly dissociated) and no where near i = 3. Then 0.38(for none)/1.15(for complete) = about 0.33 and I called 1/3 moderate; however, this is a judgement call and you may be right at barely dissociated. One never knows exactly what is meant by "barely" and "moderately". I don't think you are confused at all; I think you have thought it through very well. You could make a case for 50% being moderate.

I just wanted to say thanks for all your help! I'm still thinking about what to do for seven, but you make a good point. Your way makes more sense than mine did! Thanks again! You're amazing!