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Im trying to find the Molar concentration of substance B in a .174L solution. Given...

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tikclocktok | (Level 2) eNoter

Posted September 19, 2013 at 12:58 AM via web

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Im trying to find the Molar concentration of substance B in a .174L solution.

Given that a balanced equation is (sub A) + 2(sub B) ------> (some balanced stuff here)

sub A molarity is 0.1

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llltkl | College Teacher | (Level 3) Valedictorian

Posted September 19, 2013 at 2:23 AM (Answer #1)

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Usually, concentration of one of the substances in solution is determined by titration with a substance of known concentration, that reacts with it cleanly.

When they react in 1:1 ratio, the relationship between their concentration (in molarity) and volume is:

`V_1S_1=V_2S_2` --- (i)

Out of the four parameters f the reltion, any unknown parameter can be evaluted if rmaining three are known.

But as exemplified in the given reaction, when they react in 1:2 ratio, the relationship between their concentration (in molarity) and volume takes the form:

`2V_AS_A=V_BS_B` --- (ii)

Thus, if three of the parameters are known, the unknown one can be determined.

In the given example, two are given. So, a third parameter has to be determined first through titration, only then the relationship (ii) would yield the fourth parameter.

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