Make a solution of 10,000ppm hypochlorite

[soconfused]

I have to make a solution of 10,000ppm hypochlorite, since 1ppm is like 1mg/l for a solute in water solution. Does this mean that i have to add 10,000mg hypochlorite in 1liter water? If hypochlorite is in a liquid form, should i take into account its density and from that to find the volume i add to the water to get a totol of 1 litre?

 

Besides; Is 1ppm the same like 1mg/l ? Or does it depend in other factors like both the densities of the solute and solvent?

 

 

 

Thanks for any inputs.

[Xavier]

When parts per million (ppm) is used as a unit, there should be an indication as to what phase the solute and solvent are in e.g. w/v - 1 unit of weight of solute in 1,000,000 volume units of solvent but where that is not mentioned there is an implication that the solute and solvent should be in the same phase. As this is the case in your example, you can just dilute the hypochlorite by 10,000 in 1,000,000 in water, or 1%.

 

If the hypochlorite were in powder form and you were instructed to make a solution of 10,000ppm w/v then you'd compare the basic S.I. unit for the different phases; for volume, litres and for mass(a.k.a. weight) this is kilograms (that is is not grams is a special brand of madness brought to us by the French). Therefore the dilution is of 10,000 KG of hypochlorite per 1,000,000L of water, or 10G/L.

 

However 1p.p.m. could be interpreted as 1 molecule of solute per million molecules of solvent (1 particle per million), rather than in bulk units. Then you would have to take the molecular masses into account:

1 p.p.m. = (mol.mass of solvent)/(mol.mass of solute) mG/L

 

Which interpretation is meant is not stated. It seems that you must guess from context. In the example presented, the former is intended whilst in air pollution figures the latter is clearly meant.

[soconfused]

but where that is not mentioned there is an implication that the solute and solvent should be in the same phase. As this is the case in your example, you can just dilute the hypochlorite by 10,000 in 1,000,000 in water, or 1%.

What is the unit of 10,000 and 1,000,000 in this case? mL or L? Should i not consider the densities of both solute and solvent when both are in the liquid phase?

 

Besides the one i use is Sodium hypochlorite (NaOCl), with a stock concentration of 12% . Will you please show me how to calculate 10,000ppm hypochlorite from a 12% stock? It just says the vapor density and not the density for the solution.

 

1 p.p.m. = (mol.mass of solvent)/(mol.mass of solute) mG/L

Do you mean; 1 p.p.m. = (mol.mass of solvent)/(mol.mass of solute) x mG/L? It seems like you forget something before mG/L, because i don't understand the formula.

 

Thanks.

[jdurg]

I'd say that the best way to do this calculation is based on weight. So 10,000 ppm hypochlorite in terms of weight would mean that per million grams of solution, 10,000 would be hypochlorite. Since your solvent is water, finding the density and relating that to molarity would be the easiest thing.

 

One mole of NaOCl weighs 74.45 grams. 51.45 grams of that is the OCl- ion. So if you do the 10,000 grams of OCl- per million grams of solution, you would first need to calculate how many moles of OCl- you need to get 10,000 grams of the ion. So 10,000 divided by 51.45 = 194.3635 moles of the ion. Since you can't just add the OCl- ion, you need to now figure out how much mass 194.3635 moles of NaOCl weighs. That calculation turns out to be ~14,470.3596 grams. So you take this weight and subtract if from the 1,000,000 grams of total solution which leaves you with 985529.6404 grams of water. With a density of 1g/mL, you get a volume of 985.5296 liters of water. So you now see that your final solution will have 194.3635 moles of NaOCl per 985.5296 liters of water. That's a molarity of 0.19722 Molar. It should now be no problem to calculate how much NaOCl solution you need to use to get a final concentration of 0.19722 M which equals 10,000 ppm NaOCl by weight.

[soconfused]

The stock i bought is defined in 12% and not in molarity.

 

Any ideas?

[jdurg]

Is that % by mass? Because if it's 12% by mass, it means that for every 100 grams of solution you have 12 grams of sodium hypochlorite. With that information, you should be able to easily figure out the molarity you need.