TBR Buffers Q # 56

[Sammy1024]

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I read the answer but I'm a little confused by what they're saying. Can someone explain this? Thank you!

 

[BerkReviewTeach]

The answer points out that it's basically asking how many mL of 0.4M H2SO4 would result in the same numbers of moles of H+ as 25 mL of 0.6M H3PO4. They convert to mmoles of H3PO4 and then do a basic N1V1 = N2V2 relationship. Is it unclear how the 25mL of 0.6M H3PO4 becomes 45 mmoles?

 

[Sammy1024]

How do you know that it's asking about the 0.6 M H3PO4?

 

[BerkReviewTeach]

How do you know that it's asking about the 0.6 M H3PO4?

The moles of H+ in the H2SO4 solution = The moles of base added = The moles of H+ in the H3PO4 solution.

That's what's emphasized in the start of the explanation. I think it might be worthwhile to upgrade the version of the book you have to a version from within the last four years. The explanations were revamped in early 2011, and it seems your version is from 2010 or earlier. There are plenty of used versions floating around from 2012 or later.