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I would really appreciate if you help with some Chem AP problems.

Here we go:


1) AlCl3 dissolves in water. Which contributes to this process?
a) the enthalpy of the system increases
b) the entropy of the system decreases
c) the free energy of the system increases
d) the heat of hydration of the Al+3 ion is high

2) The best molecular formula for sulfur in its naturally occurring state is
a) S b) S2 c) S6 d) S8

3) Which phase change would be expected to produce the largest decrease in enthalpy?
a) evaporation b) sublimation c) freezing d) melting e) condensation

4) The three best general tests that will help distinguish an organic solution from an inorganic solution is?
a) flammability, solubility, conductivity
b) flammability, starch, litmus
c) color, starch, conductivity
d) density, solubility, litmus

5) The oxidation on nitrogen in [N=C=O]- is?
a) +1 b) -1 c) 0 d) -2 e) +3

6) A solution forms a precipitate upon addition of NaOH solution. WHen the precipitate is dissolved in HCl and treated with KCNS solution, a deep-red color is observed. The original solution probably contained the cation

a) Fe+2 b) Cr+3 c) Fe+3 d) Mn+2

7) A precipitate forms when HCl is added to an aqueous solution, but the precipitate dissolves when a small amount of hot water is added. The original solution probably contained the cation

a) Ag+1 b) Pb +2 c) Hg2+2 d) Hg+2

8) Which air pollutant is colored?
a) CO b) NO2 c) SO2 d) SO3

By Mo222 (Mo222) on Monday, October 06, 2003 - 12:05 pm: Edit

8) NO2 I think is a brown gas.

By Mo222 (Mo222) on Monday, October 06, 2003 - 12:07 pm: Edit

4) A ??

By Mo222 (Mo222) on Monday, October 06, 2003 - 12:17 pm: Edit

1) A
2) D
3) E
4) A
5) ? I thought it would be -3.
6) ?
7) D
8) B

By Mo222 (Mo222) on Monday, October 06, 2003 - 12:21 pm: Edit

Im not sure if any of them are right. I would really appreciate if you would look at my thread "CHEM HELP" if you have a chance!

By Njboe (Njboe) on Monday, October 06, 2003 - 04:06 pm: Edit

people help!!

By Njboe (Njboe) on Monday, October 06, 2003 - 08:35 pm: Edit

HELPHELPHELPHELPHELPHELP

By Njboe (Njboe) on Wednesday, October 08, 2003 - 06:07 pm: Edit

come on some chem geniuses out there

By Mitodnaman (Mitodnaman) on Wednesday, October 08, 2003 - 06:17 pm: Edit

number 5 is b.

O is always -2, except in per oxide where it is -1
C can be +4 or -4, so, in this case =4
since the over all charge is -1, Nitrogen has to be -1 to make the net charge -1.