Volume of NaOH needed to neutralize H3PO4

[fghtffyrdmns]

Homework Statement

what volume of 0.350 mol/L NaOH(aq) is required to completely neutralize 54.5 mL of 1.31 mol/L H3PO4(aq)?

Homework Equations

c1v1 = c2v2

The Attempt at a Solution

You would just solve for v2 but I am not getting the right answer for some reason.

 

[Borek]

Blindly using equations that don't fit the problem won't get you far.

Have you tried to write reaction equation?

Also, this page may help: http://www.titrations.info/titration-calculation

 

[fghtffyrdmns]

Blindly using equations that don't fit the problem won't get you far.

Have you tried to write reaction equation?

Also, this page may help: http://www.titrations.info/titration-calculation

The equation is wrong?

 

[Borek]

Yes, the equation is wrong.

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[fghtffyrdmns]

Elaborate.

 

[Borek]

No, you follow my earlier advice - write reaction equation & read the page linked to.

 

[fghtffyrdmns]

so, 3c1v1 = c2v2

then v1 = c2v2/3c1 ?

This would give me 6.80x10^-2 L.

 

[Borek]

You got it reversed.

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[fghtffyrdmns]

You got it reversed.

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www.titrations.info, www.chemistry-quizzes.info, www.ph-meter.info

But I'm trying to find the volume of NaOH. There's 3:1 ratio.

 

[Borek]

68 mL is not a correct volume of NaOH.

 

[fghtffyrdmns]

68 mL is not a correct volume of NaOH.

Yes, I learned the hard way.

I wrote the balanced equation of H3PO4 + 3 NaOH -> 3 H2O + Na3PO4

3CnaohVnaoh = Ch3po4Vh3po4

Is this wrong?

 

[Borek]

Yes, this is wrong. You got it reversed.

How many moles of NaOH needed to react with one mole of H₃PO₄? What shoudl be multiplied by three - number fo moles of NaOH, or number of moles of H₃PO₄?

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[fghtffyrdmns]

Yes, this is wrong. You got it reversed.

How many moles of NaOH needed to react with one mole of H₃PO₄? What shoudl be multiplied by three - number fo moles of NaOH, or number of moles of H₃PO₄?

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www.titrations.info, www.chemistry-quizzes.info, www.ph-meter.info

The H₃PO₄. This way you would have a 1:1 ration, correct?

 

[Borek]

Hard to say what you mean.

Ratio of 1:1 - what to what?

 

[fghtffyrdmns]

If you multiply the H3PO4 by 3, you would have a ratio of 1:1 with NaOH3PO4.

So you could write c1v1=3c2v2?

 

[Borek]

If 1 is NaOH and 2 is H₃PO₄ then yes. But you should be more specific, as what you have wrote is ambiguous.

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