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Mole Ratio: Whole Number Ratios vs. Decimal Ratios

Posted: Fri Sep 23, 2016 12:14 pm
by Yasmine Choroomi 2C
Hi! I got this question while looking at F9 in the textbook by the way. So I know that you cant have decimals when writing empirical formulas, but are you allowed to when it asks for the mole ratio? Also when writing the mole ratio does it matter whether you put it in whole numbers or leave it as a decimal? The solutions manual left it as a decimal ratio but I accidently changed it to whole numbers. Is that alright?

Re: Whole Number Ratios vs. Decimal Ratios

Posted: Fri Sep 23, 2016 2:51 pm
by Franklin Kong 3D
If it's asking for a mole ratio, then leaving it in decimal form should be alright, as I've seen a few examples of mole ratios that are in decimal form. If you change it to whole numbers, that's also fine.

Re: Mole Ratio: Whole Number Ratios vs. Decimal Ratios

Posted: Fri Sep 30, 2016 8:45 pm
by Yamilex Velgara 2I
I had a similar question, but mine was for F21. When calculating the molar ratios for the empirical formula, my numbers were slightly different than the ones in the solutions manual, but I kept them that way until the end of the problem. I had 8.07 mol C (8.18 in solutions), 12.94 mol H (13.0 in solutions), 1.00 mol N, and 2.00 mol O. The multiple to convert from empirical formula was 6.07 (6 in solutions). For molar ratios, I usually round if the number is very close to the next whole number, but when I did this for this problem, I ended up with a different subscript for C.

Should I be rounding for molar ratios when it comes to converting from empirical formula, or should I leave them as decimals? And when multiplying the empirical formula by a factor, should we use whole numbers or decimals?

Re: Mole Ratio: Whole Number Ratios vs. Decimal Ratios

Posted: Sat Oct 01, 2016 2:32 pm
by Tiffany Chen 3E
You might want to recheck your calculations, when I did this problem mine matched the solutions manual. For example for C- 1.11 mg/12.01 g/mol= .0924 mmol. Divide that by 0.0113 mmol (the mmoles of N which was the smallest number out of the four) gives you 8.18 for C. Multiply that by 6 and you get C49. I feel that it might be best to stick with whole numbers to get the empirical formula. How did you find the multiple to convert to the empirical formula?