LikeA'13OSS Posted April 13, 2012 Report Share Posted April 13, 2012 I have 50 cm3 of sodium thiosulfate at 0.2 mol/dm3. If i used 30 cm3 of it and added 20 cm3 of water, whats the new concentration? Thanks for your time Link to post Share on other sites More sharing options...
LMaxwell Posted April 13, 2012 Report Share Posted April 13, 2012 (edited) 50cm3 sodium thio. with 0cm3 water = 0.2 mol/dm330cm3 sodium thio. with 20cm3 water = 0.12 mol/dm3Calculation: 50cm3 = 100%, therefore 30cm3 = 60%.(60/100) x 0.2 mol/dm3 = 0.12 mol/dm3.You can use the same method to calculate the concentrations at other volumes.Hope this helped,brofessionalp.s. I always doubt my maths, but I think this is correct. Edited April 13, 2012 by brofessional 1 Link to post Share on other sites More sharing options...
Sandwich Posted April 13, 2012 Report Share Posted April 13, 2012 That's not quite right - for example if you had a sip out of a glass of salt water, you wouldn't expect the remaining water to become less salty. In a similar way, using some of a solution isn't the same as diluting it. If you use 30cm3 of 0.2mol/dm3 then the remaining stuff would still be 0.2mol/dm3. You've not diluted it in any way, and as the solution is of an equal concentration throughout to begin with, removing some of it won't change the overall concentration, it just means you have less of it. You'll have less mols of sodium thiosulphate if you dried it out and looked at how much you had, but PER DM3 it's the same concentration.So the only equation is to work out what would happen if you diluted 30cm3 of 0.2mol/dm3 with 20cm3 water. THIS time you're diluting it, so the concentration will change. 1 Link to post Share on other sites More sharing options...
ILM Posted April 13, 2012 Report Share Posted April 13, 2012 To end the confusion, you are taking 30 cm3 of 0.2 thiosulfate and add 20 cm3 of water to it, so:C1V1= C2V20.2*30= C2*500.6*0.2= C2C2= 0.12 1 Link to post Share on other sites More sharing options...
Survival Robot Posted April 13, 2012 Report Share Posted April 13, 2012 Automatic generated message This topic has been closed by a moderator. Reason: Question answered. If you disagree to this action, please report this post, and a moderator or administrator will reconsider it. Kind regards, IB Survival Staff Link to post Share on other sites More sharing options...
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