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### Topic: (Preparation of solutions and dilutions)  (Read 3919 times)

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#### tm975

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##### (Preparation of solutions and dilutions)
« on: February 28, 2012, 07:59:10 PM »
Hi

This is my first post and Im struggling with these 2 questions (even though they are frustratingly simple) can someone help me out with working?

1) Calculate the number of grams of sucrose (MW 342) you would need in order to make 500ml of a 2.5mM solution.

2) Concentrated HCL (MW 36.5) is 11.6 M. Calculate the volume you would need to dilute to about 200ml to give a 10% (w/v) solution of HCL

Cheers
« Last Edit: February 28, 2012, 08:10:47 PM by tm975 »

#### tm975

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##### Re: Ahhh, desperate help needed with 2 questions
« Reply #1 on: February 28, 2012, 08:05:44 PM »
Do I use molarity for question 1? and do I convert from mM to M?

#### Arkcon

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##### Re: Ahhh, desperate help needed with 2 questions
« Reply #2 on: February 28, 2012, 09:43:52 PM »
Do I use molarity for question 1? and do I convert from mM to M?

Yes, you do use the molarity.  As for converting M to mM, you've used the 'm' before, as in mm or mL or mg, so you just divide.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

#### tm975

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##### Re: (Preparation of solutions and dilutions)
« Reply #3 on: February 28, 2012, 10:11:23 PM »
Would you be able to walk through the working with me? I got 0.00125 the first time and 0.4275 the second

#### Borek

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##### Re: (Preparation of solutions and dilutions)
« Reply #4 on: February 29, 2012, 03:48:57 AM »
I got 0.00125 the first time