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2009 DAT Gen Chem Normalcy question (#44)

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Lauren:Pre-Dent

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Hello, #44 on the 2009 DAT reads "If 50mL of H2SO4 required 50 mL of 1.0M NaOH for a complete neutralization reaction, according to the equation shown below, what would be the molarity of the acid?
2NaOH + H2SO4—> Na2SO4 +2H2O " the correct answer is B 0.5

I understand how to use the normalcy equation n1M1V1+n2M2V2 , but why do I not have to take into account the coefficients in the equation???
 

Lauren:Pre-Dent

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I set up the equation
n1M1V1=n2M2V2
(1)(1.0M)(.05L)=(2)(M2)(.05L)
where M2=molarity of the acid=0.5

I just don't get why I do not have to consider the equation coefficients where there is a 2 in front of the OH— thank you!
 

Meeza

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It's simply a balanced equation, representing the ratio of each reactant and product, and therefore wouldn't affect your calculation. Since molarity was already provided, it isn't necessary to calculate it (molarity is just moles/L). :)
 
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bodmon

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in this case its easier to approach it through logic and realize that both solutions have the same volume.
Since moles and volume are equal across both solutions, yet one is a diprotic acid, it must have half the concentration as the base
 
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