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Diluting HCl issues ? watch

1. How would I dilute a solution of HCL with concentration of 2.00 mol Dm-3 to 0.02dm-3 for a titration experiment ?
2. Using volumetric pipette, measure a known quantity (25cm^3 say) into a 250 cm^3 volumetric flask. Using distilled water, fill the volumetric flask. this dilutes to 1/10th original concentration. Repeat it once with a clean pipette to get to 1/100th of the concentration
3. Remember that when you have a concentration, you actually have a measure of whatever it is you have dissolved in water. So 2.00 moldm-3 is 2 moles of HCL per 2dm3 of water. If you want to make the concentration smaller, you need to alter that ratio so that there's now more water compared with HCL than in the original. Do you see where I'm going with this?
4. (Original post by HRR)
Remember that when you have a concentration, you actually have a measure of whatever it is you have dissolved in water. So 2.00 moldm-3 is 2 moles of HCL per 2dm3 of water. If you want to make the concentration smaller, you need to alter that ratio so that there's now more water compared with HCL than in the original. Do you see where I'm going with this?
I think I get where you're going, so say if I used 2.5cm3 of HCL and added distilled water to make it up to 250cm3 would that make it 0.02dm3 ?
5. (Original post by an_atheist)
Using volumetric pipette, measure a known quantity (25cm^3 say) into a 250 cm^3 volumetric flask. Using distilled water, fill the volumetric flask. this dilutes to 1/10th original concentration. Repea
t it once with a clean pipette to get to 1/100th of the concentration
I understand this but how would I do this practically? Would I need to take 25cm3 of the first sample out the volumetric flask then place it in another flask and fill it with distilled water to 250cm3 ?
6. (Original post by Hmb28)
I understand this but how would I do this practically? Would I need to take 25cm3 of the first sample out the volumetric flask then place it in another flask and fill it with distilled water to 250cm3 ?
Yes
7. If you want to go a little further and understand the principles behind it, strong acids can interact with the water molecules and change its volume (it's quite significant if you're using concentrated sulfuric acid), which is why you can't just dump 10ml of HCl into 990ml of water to dilute it by a factor of 100.

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