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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Shadow on October 10, 2013, 01:12:53 PM

Title: Law of equivalents
Post by: Shadow on October 10, 2013, 01:12:53 PM: I got very confused by studying this. I could really use some good explanation. For example, the equivalent unit of K₂Cr₂O₇ is 1/6K₂Cr₂O₇. If in a solution n_{K₂Cr₂O₇}=0.1mol, we should have 6 times more of 1/6K₂Cr₂O₇ because 6*1/6=1, but it's not true. Please help :'(.
Title: Re: Law of equivalents
Post by: magician4 on October 10, 2013, 02:46:17 PM: labelling "equivalent" without specifying what something should be equivalent to is meaningless

hence your confusion

your example would be relevant in redox reactions with K₂Cr₂O₇, where each chromium went from + VI to + III , and the substance oxidized would supply one electron each: here the molar ratios, i.e. "the equivalent" would be 1:6
... but you have to specify this

regards

Ingo
Title: Re: Law of equivalents
Post by: Shadow on October 11, 2013, 07:24:28 AM: That's not the point of my confusion. I have meant for the situation you wrote.
Now, can you explain the thing I asked at the beginning?
Title: Re: Law of equivalents
Post by: Borek on October 11, 2013, 08:11:34 AM: Quote from: Shadow on October 10, 2013, 01:12:53 PM
I got very confused by studying this. I could really use some good explanation. For example, the equivalent unit of K₂Cr₂O₇ is 1/6K₂Cr₂O₇. If in a solution n_{K₂Cr₂O₇}=0.1mol, we should have 6 times more of 1/6K₂Cr₂O₇ because 6*1/6=1, but it's not true. Please help :'(.

Unless I am missing something, you got it reversed. If it is 1/6, then to get 1 equivalent you need 1/6 of the mole, not 6 moles.