Mole ratios

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lasarro
Posts: 55
Joined: Thu Jul 11, 2019 12:15 am

Mole ratios

Postby lasarro » Mon Sep 30, 2019 8:19 pm

If you have 0.018 mol NaCl in a NaCl + H2O solution, you also have to have 1 mol of NaCl and 1 H2O because of the stoichiometric coefficients. How can this be possible if you only have 0.018 mol NaCl present in the solution, but you have to have at least 1 mol of NaCl for the solution?

Zaynab Hashm 2I
Posts: 69
Joined: Wed Sep 11, 2019 12:15 am

Re: Mole ratios

Postby Zaynab Hashm 2I » Mon Sep 30, 2019 8:25 pm

If you're asking about the coefficients you get from balancing equations, I believe these are just ratios used to determine relations between reactants and products. They aren't in fact the actual amount of how much you have of each reactant or product.

Alex Tchekanov Dis 2k
Posts: 81
Joined: Sat Aug 24, 2019 12:16 am

Re: Mole ratios

Postby Alex Tchekanov Dis 2k » Mon Sep 30, 2019 8:29 pm

From what I understand, the coefficients mean the ratio between the about of NaCl and H20 is 1 mole to 1 mole. Therefore, in your example, if you have 0.018 moles of NaCl, you would need 0.018 moles of H20 to ensure that there is no limiting reactant. However for example, if it was NaCl + 2H20, you would need to have 0.036 moles of water, because the ratio is now 1 to 2.

Jasmine 2C
Posts: 119
Joined: Wed Sep 18, 2019 12:18 am

Re: Mole ratios

Postby Jasmine 2C » Mon Sep 30, 2019 8:38 pm

If I am not wrong, things like balanced equations and empirical/molecular formulas need to contain whole numbers. But for what you asked about "you have 0.018 mol NaCl in a NaCl + H2O solution", I think that you can have 0.018 mol of a certain compound because 1 mole doesn't mean 1 atom (from the equation N=n*Na, or number of objects = amount in moles x Avogadro's constant); so 1 mole actually means a lot of atoms. I think it is just that the amount of NaCl isn't as much as the balanced equation, which I think is more for reference. To clarify my explanation, I think of it as:
The balanced equation is NaCl + H20 (which I assume is only one side of the equation). So essentially, the molar ratio you need for the reaction is 1:1. No matter how much you input for NaCl, you should put the same for H20 or else one of those would be a limiting reactant because you have an excess of one. So if you have 0.018 moles of NaCl, then you would need 0.018 moles of H20 for that reaction to work. As long as the ratio is 1:1 (it can be 2.5 moles of NaCl and 2.5 moles of H20), then I believe you should be good.
I hope I'm not going all over the place with my answer! :( Hope this helps!

Kayla Maldonado 1A
Posts: 64
Joined: Sat Aug 17, 2019 12:16 am
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Re: Mole ratios

Postby Kayla Maldonado 1A » Mon Sep 30, 2019 8:49 pm

You might be referring to the molar ratios found in the empirical formula in saying 1 mol of NaCl to 1 mole of H2O after balancing the equations using stoichiometric coefficients. In saying 0.018 mol NaCl and then referring to the 1:1 ratio, this also implies that there is 0.018 mol of H2O.


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