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calculation help please
2004-08-16 12:38:47
Greetings,
My basic chemistry is quite rusty, and I don't have my old college text any longer. I need to know what amount of sodium bicarbonate (in milligrams) would be needed to increase the concentration in one liter of pure water from 0 ppm to 10 ppm. I performed a very crude experiment... I took 50 ml. of purified water (.5 ppm TDS or total dissolved solids) with a pH of ~5.3 and added a very tiny spec of baking soda. The resulting TDS was ~11 ppm. The pH of the water was raised to 6.9. So now I am trying to figure out (since I don't have a scale with enough accuracy) how much baking soda was added, and then convert that to a meaningful number -- how many milligrams would I add to a liter of water to achieve the same result? I know: molecular weight of one mole of H20 = 18.0152 grams molecular weight of one mole of baking soda (NaHCO3) is 84.00687 grams 50 ml of water = ~2.7754 moles of H20 I remember avagadro's constant is 6.02 x 10e23. I don't remember my algebra very well to get this relationship figured out. Can anyone help re-educate me? -Bob V.
2004-08-18 10:42:48
one thing to remember is that ppm is the same kind of relationship as
percent, just on a much smaller scale. you do a weight to weight comparison of the two, or in the case of water only, you can do a weight to volume comparison because the density of water is 1 mg/mL. you have 1 L of water, which is 1000 mL. ppm is ug/mL (micrograms per mililiter) and it is correspondingly mg/L, so you will need 10 mg of sodium bicarbonate to make a 10 ppm solution in 1 L. b "Bob Vineyard" news:yoidnVlcvN2kkLzcRVn-jQ@comcast.com... > Greetings, > > My basic chemistry is quite rusty, and I don't have my old college text > longer. I need to know what amount of sodium bicarbonate (in milligrams) > would be needed to increase the concentration in one liter of pure water > from 0 ppm to 10 ppm. > > I performed a very crude experiment... I took 50 ml. of purified water (.5 > ppm TDS or total dissolved solids) with a pH of ~5.3 and added a very tiny > spec of baking soda. The resulting TDS was ~11 ppm. The pH of the water > raised to 6.9. So now I am trying to figure out (since I don't have a > with enough accuracy) how much baking soda was added, and then convert > to a meaningful number -- how many milligrams would I add to a liter of > water to achieve the same result? > > I know: > molecular weight of one mole of H20 = 18.0152 grams > molecular weight of one mole of baking soda (NaHCO3) is 84.00687 grams > 50 ml of water = ~2.7754 moles of H20 > > I remember avagadro's constant is 6.02 x 10e23. > > I don't remember my algebra very well to get this relationship figured > > Can anyone help re-educate me? > > -Bob V. > >
2004-08-20 14:34:59
PH is always positive from 1 to 14.
Daniel Bob Vineyard wrote: > Greetings, > > My basic chemistry is quite rusty, and I don't have my old college text any > longer. I need to know what amount of sodium bicarbonate (in milligrams) > would be needed to increase the concentration in one liter of pure water > from 0 ppm to 10 ppm. > > I performed a very crude experiment... I took 50 ml. of purified water (.5 > ppm TDS or total dissolved solids) with a pH of ~5.3 and added a very tiny > spec of baking soda. The resulting TDS was ~11 ppm. The pH of the water was > raised to 6.9. So now I am trying to figure out (since I don't have a scale > with enough accuracy) how much baking soda was added, and then convert that > to a meaningful number -- how many milligrams would I add to a liter of > water to achieve the same result? > > I know: > molecular weight of one mole of H20 = 18.0152 grams > molecular weight of one mole of baking soda (NaHCO3) is 84.00687 grams > 50 ml of water = ~2.7754 moles of H20 > > I remember avagadro's constant is 6.02 x 10e23. > > I don't remember my algebra very well to get this relationship figured out. > > Can anyone help re-educate me? > > -Bob V. > >
2004-08-21 17:10:13
Daniel Pelchat
: PH is always positive from 1 to 14. : Daniel Almost always, pH is between 1 and 14, but these are not absolute limits. Say, someone dissolves 1 mole (~40g) of NaOH in 1 liter of water. The pH of this would be 14. But you probably could put more NaOH in the solution which would drive the pH higher. Same thing on the other end, put 1 mole of HCl in a liter of water you'll get a pH of zero. But you could add more HCl and drive the pH below zero. Know that pH is logarithmic, every pH unit represents a factor of 10. So someone puts 40 grams of NaOH in a liter of water, the pH will be 14. If they only put 4 grams in the pH would be 13. Dilute this by a factor of 10, like pouring out 90 percent of the solution and replacing it with water, the pH would be 12. Hope this makes at least some sense from someone who might be hung over from a little too much C2H5OH last night.
2004-08-22 11:11:24
Nomen Nescio
: So someone puts 40 grams of NaOH in a liter of water, the pH will be 14. : If they only put 4 grams in the pH would be 13. Dilute this by a factor : of 10, like pouring out 90 percent of the solution and replacing it with : water, the pH would be 12. I did a little experimenting around with this yesterday. Mixed of a soulution which would have had about 1/2 gram of NaOH per liter. Doing a calculation like the above, I'd come up with a pH of 12.2. After very carefully putting a drop on my tongue, its seemed pretty harmless. Drank a little of it, it didn't taste much different than a solution of baking soda. I was having some heartburn, I wasn't sure how much this helped. but it might have helped a little. But it seems this would be a good antacid because the most basic of chemisty explains what it'll do with stomach acid. And unlike baking soda, it won't pruduce a bunch of unwanted C02 gas.
2004-08-25 07:54:28
I understand your reasoning on this, but your assumptions below seem to
include the sodium bicarbonate at the same density of water. Doesn't the difference in molecular weight impact this equation? -bob v. "b" > one thing to remember is that ppm is the same kind of relationship as > percent, just on a much smaller scale. you do a weight to weight > of the two, or in the case of water only, you can do a weight to volume > comparison because the density of water is 1 mg/mL. you have 1 L of > which is 1000 mL. ppm is ug/mL (micrograms per mililiter) and it is > correspondingly mg/L, so you will need 10 mg of sodium bicarbonate to make > 10 ppm solution in 1 L. > > b > > > "Bob Vineyard" > news:yoidnVlcvN2kkLzcRVn-jQ@comcast.com... > > Greetings, > > > > My basic chemistry is quite rusty, and I don't have my old college text > any > > longer. I need to know what amount of sodium bicarbonate (in milligrams) > > would be needed to increase the concentration in one liter of pure water > > from 0 ppm to 10 ppm. > > > > I performed a very crude experiment... I took 50 ml. of purified water > > ppm TDS or total dissolved solids) with a pH of ~5.3 and added a very > > spec of baking soda. The resulting TDS was ~11 ppm. The pH of the water > was > > raised to 6.9. So now I am trying to figure out (since I don't have a > scale > > with enough accuracy) how much baking soda was added, and then convert > that > > to a meaningful number -- how many milligrams would I add to a liter of > > water to achieve the same result? > > > > I know: > > molecular weight of one mole of H20 = 18.0152 grams > > molecular weight of one mole of baking soda (NaHCO3) is 84.00687 grams > > 50 ml of water = ~2.7754 moles of H20 > > > > I remember avagadro's constant is 6.02 x 10e23. > > > > I don't remember my algebra very well to get this relationship figured > out. > > > > Can anyone help re-educate me? > > > > -Bob V. > > > > > >
2004-08-25 07:58:32
Hi, you are of course correct that pH is always positive... in my post I
used the tilde as a symbol for "approximately," not as a negative sign. Sorry for any confusion. -bob v. "Daniel Pelchat" news:mvrVc.26075$Mt5.1415304@wagner.videotron.net... > PH is always positive from 1 to 14. > > Daniel > > Bob Vineyard wrote: > > > Greetings, > > > > My basic chemistry is quite rusty, and I don't have my old college text > > longer. I need to know what amount of sodium bicarbonate (in milligrams) > > would be needed to increase the concentration in one liter of pure water > > from 0 ppm to 10 ppm. > > > > I performed a very crude experiment... I took 50 ml. of purified water > > ppm TDS or total dissolved solids) with a pH of ~5.3 and added a very > > spec of baking soda. The resulting TDS was ~11 ppm. The pH of the water > > raised to 6.9. So now I am trying to figure out (since I don't have a > > with enough accuracy) how much baking soda was added, and then convert > > to a meaningful number -- how many milligrams would I add to a liter of > > water to achieve the same result? > > > > I know: > > molecular weight of one mole of H20 = 18.0152 grams > > molecular weight of one mole of baking soda (NaHCO3) is 84.00687 grams > > 50 ml of water = ~2.7754 moles of H20 > > > > I remember avagadro's constant is 6.02 x 10e23. > > > > I don't remember my algebra very well to get this relationship figured > > > > Can anyone help re-educate me? > > > > -Bob V. > > > > > |
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