# Making solutions?

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#### kill00

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10+ Year Member

Ok. I had a question regarding making solutions in lab.

Lets say I need to make 50mL of a buffer. And this buffer requires 20 mM of A, 10 mM of B, and 0.5 mM of C.

I have stock solutions of 20 mM of A, 1 M of B, and 2 M of C.

I understand how much of 1 M B that I should add, and how much of 2 M of C.

However, how much of the 20 mM do I add?

Thanks!

#### MedPR

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Ok. I had a question regarding making solutions in lab.

Lets say I need to make 50mL of a buffer. And this buffer requires 20 mM of A, 10 mM of B, and 0.5 mM of C.

I have stock solutions of 20 mM of A, 1 M of B, and 2 M of C.

I understand how much of 1 M B that I should add, and how much of 2 M of C.

However, how much of the 20 mM do I add?

Thanks!

11mL

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#### kill00

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Thanks for the answer but how did you calculate that?

#### MedPR

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Thanks for the answer but how did you calculate that?

Stoichiometry and HH.

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#### kill00

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I meant show me your work.

#### MedPR

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I meant show me your work.

No that's cheating brah.

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#### kill00

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Cool story "brah"

#### MedPR

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Cool story "brah"

Thanks brah

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#### mcloaf

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So you're asking how you can dilute a 20 mM soln to make a 20 mM soln...

#### Marshm68

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Make up a more concentrated stock of A. Problem Solved

#### kill00

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No, I'm asking how much of the 20 mM stock I should put in the 50 mL buffer soln. I realized that you're not diluting the 20 mM to 20 mM...

Also, thanks Marshm68 for actually trying to help unlike others

#### MedPR

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#### mcloaf

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Make up a more concentrated stock of A. Problem Solved

Eh, I'd probably just use the stock solution of A and dissolve B and C into it as solids if possible. Either way.

#### Marshm68

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Eh, I'd probably just use the stock solution of A and dissolve B and C into it as solids if possible. Either way.

That'd be off by like a thousandth of a percent though! Completely unacceptable!

#### MedPR

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Eh, I'd probably just use the stock solution of A and dissolve B and C into it as solids if possible. Either way.

Gotta follow instructions. No shortcuts in lab.

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#### mcloaf

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That'd be off by like a thousandth of a percent though! Completely unacceptable!

Lol, bringing back gen chem gunner memories!

#### sector9

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SDN isn't for homework help. Closing

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