Asked by bob
Calculate the oxygen ppm concentration of a 3.50 kg sample of lake water that comtains 2.34 mg of dissolved oxygen
Answers
Answered by
DrBob222
There are two very easy formula to remember for ppm. If I'm dealing with solutions I remember
1 ppm = 1 mg/L
If I'm dealing with solids (or at least with kg), I use
1 ppm = 1 mg/kg.
So ppm for this is (2.34 mg/3.50 kg) = ?
That sure makes it simple doesn't it? What do I do if the problem is not in mg and kg. Convert what I have to mg and kg and go from there. (Or convert to mg and L and go from there.).
1 ppm = 1 mg/L
If I'm dealing with solids (or at least with kg), I use
1 ppm = 1 mg/kg.
So ppm for this is (2.34 mg/3.50 kg) = ?
That sure makes it simple doesn't it? What do I do if the problem is not in mg and kg. Convert what I have to mg and kg and go from there. (Or convert to mg and L and go from there.).
Answered by
Anonymous
I got 1.5 x 10^12
Is that correct?
Is that correct?
Answered by
DrBob222
I don't know what kind of calculator you're using but I suggest you get a different one. ;-). Just in my head I can see that 2/3.5 is nowhere near 1.5E12.
2/4 is about 0.5 and 2/3 is about 0.7 so the answer MUST be somewhere in that vicinity.
2/4 is about 0.5 and 2/3 is about 0.7 so the answer MUST be somewhere in that vicinity.
Answered by
Anonymous
My calculator is perfect. In fact it is the graphing calculator i have.
I did this before and got 0.7
But i was told it was wrong
I did this before and got 0.7
But i was told it was wrong
Answered by
Anonymous
Its also because in ppm you multiply by 10^6
Answered by
DrBob222
I've always wanted a graphing calculator but never had one.
The answer is not 0.7 ppm which may be why you were told it wasn't right.
2.34 mg/3.5 kg = 0.66857 ppm which I would round to 0.669 ppm. My response above does not contain anything about multiplying by 10^6 because you don't if you use what I posted. That 1E6 is built in to the mg/kg formula. If you are intent on using the 1E6 it is done this way.
(g solute/g solution)*1E6 = ppm
So 2.34 mg is 0.00234 g.
and 3.50 kg is 3.50E3 g.
Then (0.00234/3.50E3)*1E6 = guess what? 0.669 ppm.
Your problem is simple. You took my formula, added your own modification to it (incorrectly), and came up with the wrong answer.
The answer is not 0.7 ppm which may be why you were told it wasn't right.
2.34 mg/3.5 kg = 0.66857 ppm which I would round to 0.669 ppm. My response above does not contain anything about multiplying by 10^6 because you don't if you use what I posted. That 1E6 is built in to the mg/kg formula. If you are intent on using the 1E6 it is done this way.
(g solute/g solution)*1E6 = ppm
So 2.34 mg is 0.00234 g.
and 3.50 kg is 3.50E3 g.
Then (0.00234/3.50E3)*1E6 = guess what? 0.669 ppm.
Your problem is simple. You took my formula, added your own modification to it (incorrectly), and came up with the wrong answer.
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