GC Titration...

[allard6]

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2HCl + Ba(OH)2 ---> 2H2O +BaCl2

HCl: 30 mL, 0.1 M
Ba(OH)2: 60 mL

What is the M of Ba(OH)2?

(1)(0.1)(30) = (2)(x)(60)
x = 0.025 M

My question is...

Why doesn't the coefficient "2" in front of HCl get involved in the calculation? 😕 Please let me know! Thanks! 😉

 

[Hidden]

"Ultimately it is the number of acidic H's in the acid and the number of OH's in the base and it comes from the mole ratio.
molarity = mol/L and we can make an equation out this: M = mol/V as long as we remember the volume is in liters.
Rearranging this and solving for moles yields: mol = MV.

So the following equation ultimately means (moles of acid) = (moles of base)
MaVa = MbVb

But in our case we needed 2 moles of HCl for every 1 mole of Ba(OH)2 and so the moles of acid wouldn't equal moles of base. Having twice the number of moles of acid we could instead write:
(moles acid) = 2*(moles of base) or
(1)(Ma)(Va) = (2)(Mb)(Vb)

and note that this follows our convention of naMaVa=nbMbVb.

It seems a little backwards at first which is why I tell students to use na as the number of H's in the acid and nb as the number of OH's in the base.

Hope this helps."

I was also confused by this, but here's what Chad write to clarify this

 

[allard6]

"Ultimately it is the number of acidic H's in the acid and the number of OH's in the base and it comes from the mole ratio.
molarity = mol/L and we can make an equation out this: M = mol/V as long as we remember the volume is in liters.
Rearranging this and solving for moles yields: mol = MV.

So the following equation ultimately means (moles of acid) = (moles of base)
MaVa = MbVb

But in our case we needed 2 moles of HCl for every 1 mole of Ba(OH)2 and so the moles of acid wouldn't equal moles of base. Having twice the number of moles of acid we could instead write:
(moles acid) = 2*(moles of base) or
(1)(Ma)(Va) = (2)(Mb)(Vb)

and note that this follows our convention of naMaVa=nbMbVb.

It seems a little backwards at first which is why I tell students to use na as the number of H's in the acid and nb as the number of OH's in the base.

Hope this helps."

I was also confused by this, but here's what Chad write to clarify this

Thank you so much!!! 🙂