Guest dadobi Posted August 28, 2004 Share Posted August 28, 2004 It has been a couple years since I have had drug calculations - would someone please remind me of the steps I need to answer the following questions A 7% glucose solution is made up of what % glucose and what % water?? A 20% NaCl solution is made up of what % NaCl and what % water?? thanks so much in advance Link to comment Share on other sites More sharing options...
Skye Posted August 29, 2004 Share Posted August 29, 2004 For solutions it's a weight-for-weight percentage. You would normally see this written as '7% w/w' on the bottle, for the glucose solution. This solution will then contain 7% glucose, and 93% water, by weight. But it won't equal the same percentages in volume, or in moles. Link to comment Share on other sites More sharing options...
pulkit Posted August 29, 2004 Share Posted August 29, 2004 Solutions are not always w/w, they can be v/v as well (Eg. Ethanol solutions are always v/v) when the solute is a liquid, also there are w/v solutions. 7% glucose and 20% NaCl are most probably w/v solutions. w/v is one of the most popular ways to keep track of concentration, its also called strength of a solution. Link to comment Share on other sites More sharing options...
Primarygun Posted August 29, 2004 Share Posted August 29, 2004 dadobi, if it's volume, solute/solution Be careful, the solution=solvent + solute This all my little knowledge, don't scold me if I am wrong:P Link to comment Share on other sites More sharing options...
Skye Posted August 29, 2004 Share Posted August 29, 2004 pulkit, I assume it's w/w for solutions unless it says otherwise, this is the most common I've seen. Ethanol I've seen usually w/w, i.e. most of the ethanol around the lab used for cleaning and that will be 95% w/w. But it may just be my crazy part of the world, and it wouldn't surprise me if the glucose and NaCl were w/v. Link to comment Share on other sites More sharing options...
Kedas Posted August 29, 2004 Share Posted August 29, 2004 weight/volume has an unit so it can't be in % Link to comment Share on other sites More sharing options...
pulkit Posted August 29, 2004 Share Posted August 29, 2004 weight/volume has an unit so it can't be in % True. I must acept that I am wrong. Link to comment Share on other sites More sharing options...
sfpublic Posted December 1, 2005 Share Posted December 1, 2005 Hello, I am a tiny bit confused about this w/w term. Could you please clarify it with a few examples so that I can understand it? thank you Link to comment Share on other sites More sharing options...
RyanJ Posted December 4, 2005 Share Posted December 4, 2005 Hello' date=' I am a tiny bit confused about this w/w term. Could you please clarify it with a few examples so that I can understand it? thank you[/quote'] Ok... let see if I can explain it (I am now known for my explaining abilities ) Ok, in the examples remember they must all add up too 100% so... Lets go through an examaple: Question: A solution is composed of 33.3% Nitric Acid, 21.6% Hydrochloric Acid and the rest is water. Calculate the percentage of water in the solution. Answer: Now, here is a rule, all percentages in this case must MUST add up too 100% so... [math]33.3 + 21.6 + x = 100[/math] [math]54.9 + x = 100[/math] [math]x = (100 - 54.9)[/math] [math]x = 45.1[/math] So the percentage of water is 45.1% Your examples will work the same way just remember, they just all add up to 100% Here is another incase you need a bit ore practice. Question: A composition of an alloy requires between 0.95% too 2.1% Carbon and the rest pure Iron. Calculate the percentage of Iron needed if the Carbon content is considered too be 1.3%. Answer: Now, here is a rule, all percentages in this case must MUST add up too 100% so... [math]1.3 + x = 100[/math] [math]x = (100 - 1.3)[/math] [math]x = 98.7[/math] So you need 98.7% Iron assuming that the Carbon content is 1.3% Good luck! Cheers, Ryan Jones Link to comment Share on other sites More sharing options...
sfpublic Posted January 1, 2006 Share Posted January 1, 2006 Thank you for your clear answer to the w/w question. I had forgotten that I posted it until 10 mins ago. It was one of those I-can-wait questions. Anyway, thanks andy Link to comment Share on other sites More sharing options...
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