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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: wm334 on March 01, 2017, 04:35:19 AM

If I make a 0.2g/ml solution and dissolve this in 1L, do I have 0.2g/L?
Thanks

How much of the 0.2 g/ml solution do you have?

5 ml

So if you have 5ml of 0.2g/ml solution how many grams of this substance are there? If you make that up to 1L does that change how man grams of of the active are in the 1L solution?

I think I still have 2g in both solutions, but I know if I look at molartiy this changes.

What is 5x0.2?

1

I think I still have 2g in both solutions, but I know if I look at molartiy this changes.
You know the grams, and you know the old an new volumes. How does it change?
First think: you start with some amount, you add more solvent, your final answer has to be less than it was before?
Also think, by how much less: If you had a gram, in 10 mL, and you added 90 ml more ... you'd have the same gram, but now in 100. The 100 is different from 10 by how?
Please try to put all your work, from start to finish, in one posting. Otherwise the thread will grow to multiple pages, and we'll forget what we've already done.

OK I presume 0.2g/5ml, use c1v1.. 0.2*5/1000 ml, new concentration = 0.001g/L

If I make a 0.2g/ml solution and dissolve this in 1L, do I have 0.2g/L?
I presume 0.2g/5ml
Which is correct?

0.2g/5ml

You informed us that your concentration is 0.2 g/ml. Then you added that you have 5 ml of solution.
This means that you dilute 5 ml of solution with concentration of 0.2 g/ml to 1000 ml (1L). In such a case your answer is wrong.
Or you something changed during discussion?

ok 0.2g/ml is 0.0002g/L using C1V1

OK, this is a simple 1000 times dilution.

They have an equation for such scenarios as that known as the "Dilution Equation". The equation states that if moles  or mass in your instant  of solute is kept constant then the following is true:
C_{1}V_{1} = C_{2}V_{2}
where C_{1} is the original concentration of solution, and V_{1} is original volume of solution, and C_{2} is final concentration of diluted solution, and V_{2} is final volume of diluted solution.
You know all but final concentration (in g/mL)  rearrange to find final concentration.
KungKemi