What is the final concentration of each ion if 150mL of .50 M BaCl2
and 85mL of .75 M NaCl are mixed together? 1% is how many ppm? 1 ppm
is how many mg/L?

---

Clarification of Question by katha2017-ga on 18 Feb 2005 16:48 PST

This is a part per miilions

---

Clarification of Question by katha2017-ga on 18 Feb 2005 16:48 PST

question

Hints:

1. How many moles of Ba and Cl ions are in 150mL of a 0.50M solution of BaCl2?  
2. How many moles of Na and Cl ions are in 85mL of a 0.75M solution of NaCl? 
3. How many moles of Ba, Na, and Cl do you have if you add the two
solutions together?
4. How many liters of solution do you have if you add 150mL and 85mL together?
5. Divide the answers in hint 3 by the answer to hint 4.  That will
give you the molar concentrations of each ion in the final solution.

1% means 1 part in 100 (i.e., 0.01).  1ppm means 1 part in 1,000,000
(part per million = ppm or 0.000001).  10000ppm = 1%.  When you use
terms like ppm or % to describe the concentration of something, both
the dissolved substance (the solute) and the stuff doing the
dissolving (the solvent) have to be expressed in the same units.  A
10ppm by mass solution would contain 10 micrograms of solute for every
gram of solution.  A 350ppm by volume concentration of CO2 in the
atmosphere would contain 350 liters of CO2 in every million liters of
air.

Your last question asked how to convert ppm to mg/L.  IN this case the
solute and solvent are being expressed in different units (mg, or
units of mass for the solute, and L, or units of volume for the
solution as a whole). If you are asking about aqueous solutions, then
there is no simple way to calculate the exact answer without knowing
more about the solution.  The problem occurs because when you dissolve
things, the volume of the resulting solution is not necessarily equal
to the sum of the volumes of the things you mixed.  For instance, you
can dissolve quite a lot of table salt in water without making a large
change in the solution volume.  Sugar, however, acts more "ideally",
and a sugar solution will have about the volume of the original sugar
plus the volume of the original water.

All that having been said, you can make an approximate conversion
between ppm and mg/L for dilute aqueous (i.e., water) solutions by
knowing that 1 liter of water has a mass of 1000 gms.

ppm = (gms solute * 1,000,000)/(gms solute + gms solvent)

1,000,000/ppm = (gms solute + gms solvent)/(gms solute) 
= 1 + (gms solvent)/(gms solute)

[hit post before I finished the last comment]

ppm = (gms solute * 1,000,000)/(gms solute + gms solvent)

1,000,000/ppm = (gms solute + gms solvent)/(gms solute) 
= 1 + (gms solvent)/(gms solute)

(1,000,000-ppm)/ppm = gms solvent/gms solute.

(gms solute)/(gms solvent) = ppm/(1,000,000-ppm)

If the solution is dilute, 1 liter of solution will have a mass of
about 1000 grams, and we know that 1000 mg = 1 gm:

(mg solute)/(L solution) ~= 1000mg/g * 1000gm/Liter * ppm/(1,000,000-ppm)
mg solute/L solution ~ ppm/(1-ppm/1,000,000).