Is my Intro. to Chemistry textbook wrong? Please check.?

oschrndz · #1 (**permalink**) 03-22-2008, 09:47 PM

I think my Chemistry textbook has typos. The problem is:
- What mass in grams, of calcium is present in a 225-gram sample of pure calcium sulfate, CaSO4?

My solution:
I calculated the percentage percentage of Ca doing:
40.078 g Ca/136.14 g CaSO4 x 100% = 29.439% Ca
then,
225-g CaSO4 X 0.29439 = 66.2 g Ca <---thats my answer.

But the book's answer is:
There are 90.1 g of Calcium in a 225-gram sample of calcium sulfate?

Huh? Am I wrong?

NasukoMath · #2 (**permalink**) 03-22-2008, 09:47 PM

me too. i calculated it, and the textbook is incorrect.

really 100% you are correct

steve_geo1 · #3 (**permalink**) 03-22-2008, 09:49 PM

Atomic weights: Ca=40 S=32 O=16 CaSO4=136

225gCaSO4 x 1molCaSO4/136gCaSO4 x 1molCa/1molCaSO4 x 40gCa/1molCa = 66.2g Ca

It appears that you are correct.

Bruce J · #4 (**permalink**) 03-22-2008, 09:49 PM

I think the book is wrong. My calculations show a similar disparity.

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