Problem 11b

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christabellej 1F
Posts: 109
Joined: Sat Aug 17, 2019 12:17 am

Problem 11b

Postby christabellej 1F » Mon Sep 30, 2019 2:22 pm

This problem asks for the formula and there is 31.91% K, 28.93% Cl and the rest O2 (39.16%). When I converted these mass percentages to moles, I got roughly 1.22 mol O2, 0.82 mol Cl, and 0.82 mol K. After dividing all these moles by the lowest mol (0.82) I got that there is a ratio of 1.5 mol O2: 1 mol Cl: 1 mol K. Since the ratios need to be whole numbers, I would multiply all by 2. However, the solutions say that the formula should be KClO3. Where am I going wrong? Also how do I know what order to write the K and Cl and O? Thank you :)

Mashkinadze_1D
Posts: 87
Joined: Sat Aug 24, 2019 12:15 am

Re: Problem 11b

Postby Mashkinadze_1D » Mon Sep 30, 2019 2:51 pm

Hello! The reason you are getting the problem wrong is a small error you made with the O2. When you divided for moles you found the moles of O2, but instead it would have been more helpful to find the moles of O which is 2.4475. You would then proceed to find K:O which would be about 2.98 or close enough to get to 3. K:CL are one and therefore you would get KCLO3. If you wanted to find the moles of O2 this would also be possible but in the empirical formula you would have to take account that this is so and use the 1.5 you found x the 2 in O2 to also fin that there is 3 Oxygen atoms. Hope this solves your issue!


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