[petstar21]

1. A certain gas has a concentration of 2 Mg per 100g water, whats the concentration of gas in parts per million?
--- I know how to do this problem and the formula for ppm, however, what I dont understand is why the denominator (mass of solutin) would be 100 and  not 100g + 2 Mg (obviously youd convert to same units) to get the answer of 20.

2. WHen Temp increases, solubility solids usually increase, however, when temp decrease solubility of solids ALWAYS decrease or USUALLy decrease?

3. I used a reference table but i just didnt know what to do- 100 g water saturated with NH3 at 30 Celsius. if temperature was lowered to 0 C how much addtional NH3 would be needded to resaturate the solution?? what do I do??

4. Compared with .01 molal sugar solution, .01 m KCl solution has about 2 x the freezing depression. how do you know this?? my refernce table doesnt list it!

5. I know K= product of products/ product of reactants but what is K/ what does it stand for?

6. If system 2CO + O2 ----> 2 CO2 came to equilibrium, and more CO was added, why does CO2 increase and O2 decrease??

7. If pressure on the equilibrium system above increases, does the quantity of CO2 increase, decraese or stay the same and why?? (how does pressure affect it)

8. If temp on equilibrum sytem CH3OH + 101KJ-----> CO + 2H2 increaes, why does CH3OH decrese and CO increase??

9. if The rate evaporation from surface of liquid exceeds rate of condensation-
a. liquid boiling
b. heat energy no longer avilable
c. concentration vapor increases

10. if temp and surface area of liquyid remain constant-
a. rate of evaporation remains constant
b. rate condensation increaeses and rate evaporation decreaes
c. no further evaporation occurs
d. liquid not at equilibrium with its vapor

11. Which best describes heat
a. energy transferredd between samples of matter because of the difference in their temps
b. a measure of average kinetic energy of samples of matter (isnt that temp??)
c. energy stored in sample of matter

thanks so much, im so confused!

[Arkcon]

1. A certain gas has a concentration of 2 Mg per 100g water, whats the concentration of gas in parts per million?
--- I know how to do this problem and the formula for ppm, however, what I dont understand is why the denominator (mass of solutin) would be 100 and  not 100g + 2 Mg (obviously youd convert to same units) to get the answer of 20.

OK.  Do it your way and compare the answer.  Remember significant figures.

4. Compared with .01 molal sugar solution, .01 m KCl solution has about 2 x the freezing depression. how do you know this?? my refernce table doesnt list it!

OK.  what causes freezeing depression, and what hint can you get from the question, what is about 2X in KCl compared to sucrose?

[sjb]

As well as Arkcon's pointers, be careful how you write these things out. 1 Mg is not the same as 1 mg. 1 Mg per 100g of water is very very very concentrated (to the extent that I can't think of anything that can be that concentrated).

S

[Borek]

1 Mg per 100g of water is very very very concentrated (to the extent that I can't think of anything that can be that concentrated).

Ethanol

molarity - 17.15, so not that bad
molality - 2.17 x 10⁵ - and that's funny

[sjb]

True.

I had solids on my mind, rather than liquids. I suppose it's only semantics whether the solution you describe is aqueous ethanol, or ethanolic water.

S