albertlee Posted October 11, 2005 Share Posted October 11, 2005 Even acid has OH- ions in it...., but how can we measure how many OH- ions there are... secondly, how can we determine how many ions/molecules a solution can dissolve?? esp with water as the solvent. Eg, how many oxygen molecules, hydrogen ions, halogen ions, etc... can water dissolve? Any help?? thx alot Link to comment Share on other sites More sharing options...
jdurg Posted October 11, 2005 Share Posted October 11, 2005 Experimentation. You do an experiment and find out the answer. For solubility, you just keep adding until it will hold no more, all the while keeping track of much you have added. For the acid question, pure sulfuric acid has ZERO OH- ions in it. Pure acetic acid has none. Pure phosphoric acid has none. Hydrogen chloride gas has none. Pure HF has none. Electrically you can measure how many OH- ions are in a pure water solution. Also, in pure water, for every H+ ion there is an OH- ion. This ratio of OH- ions to water molecules is constant for pure water. Upon adding weak acids and bases, this ratio changes a bit and can be measured electrically. Link to comment Share on other sites More sharing options...
albertlee Posted October 11, 2005 Author Share Posted October 11, 2005 I am abit confused about what do you mean by "pure"... pure acid does contain water, therefore it has OH- ions in it. Secondly, how do you find out how much oxygen is dissolved in a solution?? please help thx alot Link to comment Share on other sites More sharing options...
jdurg Posted October 12, 2005 Share Posted October 12, 2005 Pure acid does NOT contain water. Tell me where the water is in pure sulfuric acid (H2SO4). Tell me where it is in pure acetic acid (CH3COOH). How about pure benzoic acid? Pure acids do not have to have water in them. For the oxygen in water, they have oxygen adsorbant materials which can absorb oxygen gas. The water is heated to drive all the gas out, and the change in mass of the adsorbant is detected. Link to comment Share on other sites More sharing options...
woelen Posted October 12, 2005 Share Posted October 12, 2005 Albertlee, take time to 'digest' the answers, given by others. If you really want to learn things, then ask a few things and if answers are given, take the time to really understand these answers. In follow up posts you can concentrate on the things which you still did not understand. An example of inappropriate use of this forum: You ask something about hydroxide in acid. You get a good answer and now in your followup you suddenly ask a question about solubility of oxygen. This behavior does not really give us the impression that you think over the answers you obtain and just shoot out random questions. Link to comment Share on other sites More sharing options...
sanjaygeorge Posted October 12, 2005 Share Posted October 12, 2005 By Ph scale we can find the conc. of H+ and OH- . pure sulphuric acid means 100% h2so4 conc. h2so4 means 98% h2so4 and 2% water. So conc. H2SO4 contain some OH- from water. Link to comment Share on other sites More sharing options...
albertlee Posted October 12, 2005 Author Share Posted October 12, 2005 An example of inappropriate use of this forum: You ask something about hydroxide in acid. You get a good answer and now in your followup you suddenly ask a question about solubility of oxygen. This behavior does not really give us the impression that you think over the answers you obtain and just shoot out random questions. Why do you think that I didnot think over the answers? aren't both questions related to "concentration of particles in a solution"? all questions actually related to an investigation I did about iron rusting under different pH. there are five sets of iron nail in testtube with different solution, and each of them is sealed with a stopper. 1, sulfuric acid 1/3M 2, sulfuric acid 2/3M 3, Sodium Hydroxide 1/3M 4, Sodium Hydroxide 2/3M 5, tap water This is what I found out, the rusting of nail under tap water is the greatest, the weaker Alkali is the second greatest, but only a little bit of rust. For the stronger acid, the nail turns completely black and for the weaker one, the nail is corroded to an extent that it becomes black powders. for the stronger alkali, nothing happens to the nail. This actually contradicts to what I thought in the beginning. I thought that alkali will increase the rate of rusting.... So I conclude that it must be the alteration of concentration of oxygen, which means that maybe there is less oxygen in alkali than in water, when the tube is sealed. The other thing goes out of expectancy is the acid, how come the weaker acid actually corrodes more?? Any help on this?? thx alot Link to comment Share on other sites More sharing options...
albertlee Posted October 12, 2005 Author Share Posted October 12, 2005 btw, I always find hard to tell the concentration of acid/alkali in %. Say 1M of acid in water, what is its concentration in %? Link to comment Share on other sites More sharing options...
albertlee Posted October 12, 2005 Author Share Posted October 12, 2005 btw, I always find hard to tell the concentration of acid/alkali in %. Say 1M of acid in water, what is its concentration in %? Link to comment Share on other sites More sharing options...
insane_alien Posted October 12, 2005 Share Posted October 12, 2005 how much water is the acid in? can't work out concentration if we don't have the volume Link to comment Share on other sites More sharing options...
albertlee Posted October 12, 2005 Author Share Posted October 12, 2005 the thing is, 1M = 1mole of acid molecules / 1L of water To me, there is no % here, because you can have 1M, 2M, 3M, ...nM... by the way, please also help me from the the post #7... thx alot Link to comment Share on other sites More sharing options...
The Thing Posted October 12, 2005 Share Posted October 12, 2005 I think that commercial acids and bases, when sold, are using the wt. % instead of the mass/volume %. Assuming that I thought correctly: [math] \frac{wt. percent*density}{MW}*10=M [/math] M=Molarity density: (I think specific gravity is given most of the time instead of density) MW=molecular weight And the % is the wt.% of the concentration. Simply rearrange the formula above. Link to comment Share on other sites More sharing options...
albertlee Posted October 12, 2005 Author Share Posted October 12, 2005 what is wt. %? and again, any one can help me according to post #7? Link to comment Share on other sites More sharing options...
Borek Posted October 12, 2005 Share Posted October 12, 2005 For % vs molarity - read about percentage to molarity conversion. Best, Borek -- Chemical calculators at www.chembuddy.com pH calculator concentration conversion Link to comment Share on other sites More sharing options...
akcapr Posted October 12, 2005 Share Posted October 12, 2005 If Conc. h2so4 gets to 18 molar concetration per liter of water, what percent is 1 M? Its 1/18 or 5.5%. It is different however for weight per liter. Link to comment Share on other sites More sharing options...
woelen Posted October 12, 2005 Share Posted October 12, 2005 No, 1 M H2SO4 is almost 10% by weight. You forget to take into account that conc. H2SO4 has a density over 1.8 gram per ml, while 1M H2SO4 is close to 1 gram per ml. Link to comment Share on other sites More sharing options...
akcapr Posted October 13, 2005 Share Posted October 13, 2005 Ya i was talking about molar percentage. I usually use that when I refer to acids, It seems more accurate for purposes. Link to comment Share on other sites More sharing options...
woelen Posted October 13, 2005 Share Posted October 13, 2005 Can you explain your reasoning to me by a worked out example for 1 M H2SO4? I do not understand what you mean. What do you mean with "molar percentage"? I just cannot get any other percentage than 10% by weight for 1 M H2SO4. If I were to look for the percentage of the number of moles of molecules, then I would find approximately 2% (pure water is 55M, we have around 10% less, so 50M and we have 1 M acid in it), but this is just arithmetic and has no real useful meaning. Link to comment Share on other sites More sharing options...
albertlee Posted October 13, 2005 Author Share Posted October 13, 2005 any one can help me according to post #7? Link to comment Share on other sites More sharing options...
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