Initial concentrations and molar ratios

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Tyler Angtuaco 1G
Posts: 130
Joined: Wed Sep 11, 2019 12:16 am

Initial concentrations and molar ratios

Postby Tyler Angtuaco 1G » Fri Jan 17, 2020 7:59 am

If you are given the initial concentration of one of two reactants in a reaction, is the only reason why we cannot use molar ratios to determine the initial concentration of the other reactant because of the possibility that one of them is a limiting reactant? Or are there more reasons to this?

Letty Liu 2C
Posts: 105
Joined: Fri Aug 09, 2019 12:16 am

Re: Initial concentrations and molar ratios

Postby Letty Liu 2C » Fri Jan 17, 2020 10:08 am

We can’t determine the initial concentration of the other reactant based off of one reactant because the moles are used for equilibrium. The initial concentrations could range from anything. This is my train of thought but I’m not completely sure.

William Francis 2E
Posts: 101
Joined: Wed Sep 18, 2019 12:20 am

Re: Initial concentrations and molar ratios

Postby William Francis 2E » Fri Jan 17, 2020 10:36 am

The moles of a substance used in a reaction may differ from the number of moles of the substance actually found in the solution. We cannot assume the concentration of a reactant based upon the concentration of another reactant because we have no idea how much of it was actually added to the solution. For instance, in the equation NH3(aq) + H2O(l) <--> NH4+(aq) + OH-(aq), even if we know that one mole of NH3 is present in the solution, it does not mean that there is only one mole of water present in the solution. In fact, the reaction clearly takes place in water as evidenced by the aqueous reactant and products.


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