BI Duck Posted February 25, 2011 Report Share Posted February 25, 2011 Hi,I have a question related to aqueous solutions.If I dilute 1M of NaCl in a given measure of water; and the water dissociates it.Will I have also 1M of ions Na+ and Cl- ? Reply Link to post Share on other sites More sharing options...
nametaken Posted February 25, 2011 Report Share Posted February 25, 2011 Yes. Reply Link to post Share on other sites More sharing options...
Drake Glau Posted February 25, 2011 Report Share Posted February 25, 2011 The concentration of the solution will equal the concentration of the dissociated ions for NaCl Reply Link to post Share on other sites More sharing options...
dessskris Posted February 25, 2011 Report Share Posted February 25, 2011 no. 1 M is the concentration. you will have different concentration of NaCl but same number of mol of NaCl.let's say in the beginning you have 0.5 mol of NaCl. when it dissociates in water, you will have 0.5 mol of Na+ and 0.5 mol of Cl- Reply Link to post Share on other sites More sharing options...
Drake Glau Posted February 25, 2011 Report Share Posted February 25, 2011 (edited) If the concentration is 0.5M that would mean there is 0.5mol of solid NaCl mixed into 1L of water. That will still yield 0.5mol of Na+ and 0.5mol of Cl- in the same volume of the water so the concentration is still 0.5M for both ions O.o Edited February 25, 2011 by Drake Glau Reply Link to post Share on other sites More sharing options...
Keel Posted February 25, 2011 Report Share Posted February 25, 2011 I think people are getting confused with the 'M'. It can mean molar as in number of moles per volume or it can mean number of moles. (although 'n' should be used for number of moles eg. nNaCl)Drake was in fact correct. The concentration of NaCl(aq)= (no. of moles of NaCl)/(volume) Reply Link to post Share on other sites More sharing options...
Drake Glau Posted February 25, 2011 Report Share Posted February 25, 2011 Side note: This only works because the ratios for the dissociation NaCl are 1:1. If the salt was...I don't know, BeCl2 then the chemical equation would be BeCl2=>Be2++2Cl- resulting in 2mol of Cl- and 1mol of Be+. Reply Link to post Share on other sites More sharing options...
dessskris Posted February 25, 2011 Report Share Posted February 25, 2011 ok so my point is...say you have 30 ml of 1 M of NaCl in the beginning.you add 20 ml of pure water.now you have 50 ml of NaCl with the same number of mol of NaCl as the reagent, but different concentration with the reagent.new [NaCl] = new [Na+] = new [Cl-] ≠ initial [NaCl]sorry to confuse you guys Reply Link to post Share on other sites More sharing options...
Keel Posted February 25, 2011 Report Share Posted February 25, 2011 (edited) sorry to confuse you guysNo, I don't think it's anyone's fault. It's the notation 'M', while Drake and I were thinking molar, you were thinking moles. Try replacing 'moles' or 'molar' into the original question; 'Moles' you get your answer which is 'yes', 'molar' you get Drake's which is 'depends on volume'. Edited February 25, 2011 by Keel Reply Link to post Share on other sites More sharing options...
dessskris Posted February 25, 2011 Report Share Posted February 25, 2011 no, Keel, I know M is molar (concentration). actually at first I was thinking that she asked whether the initial conc and the new conc would be the same. Drake and the rest were thinking that she asked whether the new NaCl conc and the new ions conc would be the same.so it's answered.new [NaCl] = new [Na+] = new [Cl-] ≠ initial [NaCl] Reply Link to post Share on other sites More sharing options...
Keel Posted February 25, 2011 Report Share Posted February 25, 2011 I completely disagree. If that was the case, why would she state "and the water dissociates it" when the salt is already dissociated in the original solution? The fist 'M' is clearly moles not molar. The question is whether the second 'M' is moles or molar. This will need clarifying. Without it, there are two interpretations to the question. 1. Will I have 1 molar Na+ and Cl-?2. Will there be one moles of Na+ and Cl- in the solution? Reply Link to post Share on other sites More sharing options...
Drake Glau Posted February 25, 2011 Report Share Posted February 25, 2011 (edited) Both of those answers are yes. It says it is a 1M solution so you will have 1M of the ions and 1mol of the ions assuming there is 1L of the solution lol Edited February 25, 2011 by Drake Glau Reply Link to post Share on other sites More sharing options...
Keel Posted February 25, 2011 Report Share Posted February 25, 2011 Both of those answers are yes. It says it is a 1M solution so you will have 1M of the ions and 1mol of the ions assuming there is 1L of the solution lol Well we can't assume! 'Yes' if the volume is 100dm3, 'No' if it is not. Plus he said in 'a given measurement of water' what are the chances that that will be 100dm3? Reply Link to post Share on other sites More sharing options...
Drake Glau Posted February 25, 2011 Report Share Posted February 25, 2011 I don't know about 100dm3 but maybe 1 I'm just messing with you now. Point to the story:[NaCl]=[Na+] and [Cl-] Reply Link to post Share on other sites More sharing options...
Keel Posted February 25, 2011 Report Share Posted February 25, 2011 That is true. However, how do you know he is asking question 1 and not 2? Couldn't the question be about the moles of ions in the solution and whether they fully disociate or not? I don't think theres any point in talking about this until he comes back and asks the the right question . Reply Link to post Share on other sites More sharing options...
Drake Glau Posted February 25, 2011 Report Share Posted February 25, 2011 M stands for molar as far as I care. By his 2nd year of HL Chem I'd hope M=Molarity by now Reply Link to post Share on other sites More sharing options...
dessskris Posted February 25, 2011 Report Share Posted February 25, 2011 FYI,Common Notations in Chemn(X) = __ molnumber of moles of X = __ moles[X] = __ Mconcentration of X = __ mol/dm3don't confuse yourselves. let the topic starter read all these replies and make things clear 1 Reply Link to post Share on other sites More sharing options...
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