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I have a $\pu{0.3 M}$ $\ce{NaCl}$ stock solution and need to create a $\pu{0.01 M}$ $\ce{NaCl}$ solution that is $\pu{50 mL}$. The only tools I am given are volumetric pipettes that are $10.0, 5.0, 1.0 \text{ and }\pu{0.5 mL}$ and $\pu{50.0 mL}$ volumetric flasks. I understand the physical process where I would measure out a specific amount and place it in the flask using the pipette(s) and then add the required amount of water.

I need to use the dilution equation $M_1\times V_1 = M_2\times V_2$ which I did and I got $\pu{1.666667 mL}$ of solution that needs to be taken from the $\pu{0.3 M}$ stock solution to create the $\pu{0.01 M}$ solution. The only problem is that I can't do that since the materials I have do not allow me to measure out that amount.

I tried to "convert" the $\pu{0.3 M}$ to various other concentrations that would hopefully get me down to $\pu{0.01 M}$ but have failed so far. I tried to find concentrations that would result in a whole number or a value with $.5$ at the end after dividing by the product from $M_1\times V_1$ but failed every time. In addition, I combined the two concentrations and found the midpoints between them and tried to use those values, but they did not work either. Where is a good place for me to start?

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Assuming you can use a beaker (or just one of those 50 ml volumetric flask for mixing), you could first dilute some of the 0.3 M solution to 0.1 M by adding 5 ml of stock to 10 ml of water. Now you have a 0.1 M solution of NaCl which you can calculate how to dilute using the M1*V1=M2*V2 equation. Doing this, I calculate that to make 50 ml of 0.01 M solution, you need 5 ml of the 0.1 M solution you made, which you can do with a pipette.

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  • $\begingroup$ Generally, the first step is not proper since adding 5 ml of a solution to 10 ml of water does not precisely yield 15 ml. $\endgroup$ – Loong Oct 21 '17 at 23:07
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This question is years old, but I went through the calculations for my own interest. The stock solution needs to be diluted to 1/30th of its original strength. Take 5 ml of it and add 5ml water, resulting in 10ml of 0.15M solution. Add 20 ml water, resulting in 30ml of 0.05M solution. Take 10ml of that, add 40 ml of water. The result is 50ml of 0.01M solution. To verify: 10 x 0.05 = 50 x 0.01 That's one way to do it.

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