(c) How many moles of water molecules are in 5.15 g of Epsom salts?
I've been told that I should multiply 7 by (5.15g/246.48mol) to obtain the number of mols of water molecules; that being said, I can't exactly pinpoint why this is the way to solve this problem. Could anyone explain step by step how you went about solving this problem? Thank you!
Homework Problem E.9c
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Re: Homework Problem E.9c
Sure! So to find the moles of H2O you follow the equation (g = mol X gmol-1 ) and divide 5.15g by the molar mass of MgSO4 x 7H20 which is 246.48 gmol-1. After this, you multiply the result (.02089 mol) by 7 because you want just one mole of water but you calculated the moles for 7. To accommodate this, you multiply .02089 mol by 7 and get 0.146 mol. Hope this helps. It's basically just looking at the ratio between what you calculated and what you want your final answer to be in terms of.
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Re: Homework Problem E.9c
The problem states that it is magnesium sulfate heptahydrate. Hepta= 7, so there are 7 molecules of H20. Therefore you must multiply by 7 in part c.
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Re: Homework Problem E.9c
APatel_4A wrote:How do you find the formula for magnesium sulfate heptahydrate?
To find the formula for magnesium sulfate hydrate, you must know the ions that magnesium and sulfate form. Magnesium always forms Mg2+ and sulfate is (SO4)2-. Therefore, magnesium sulfate is MgSO4. Hepta- is a prefix meaning 7, so there are 7 water molecules attached to a molecule of MgSO4.
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Re: Homework Problem E.9c
The problem refers to a heptahydrate and you have to account for its mass and moles when doing problems regarding it.
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