A 10.0 mL sample of a monoprotic acid is titrated with 45.5 mL of 0.200 M #NaOH#. What is the concentration of the acid?

Answer 1

#"0.910 M"#

A monoprotic acid can contribute one proton to the neutralization reaction that takes place when sodium hydroxide, #"NaOH"#, is added to the solution.
If you take #"HA"# to be the general formula of a monoprotic acid, you can say that the balanced chemical equation that describes this neutralization reaction looks like this
#"HA"_ ((aq)) + "NaOH"_ ((aq)) -> "NaA"_ ((aq)) + "H"_ 2"O"_ ((l))#

You must add the same amounts of base and acid to achieve total neutralization.

You are already aware of the molarity of the sodium hydroxide solution. Molarity is defined as the number of moles of solute present in one liter of solution.

Now, let's assume that the monoprotic acid solution has a molarity equal to #"0.200 M"#. In this case, the titration would require #"45.5 mL"# of acid solution, since solutions of equal volumes and equal molarities contain the same number of moles of solute.
However, you know that the acid solution has a volume of #"10.0 mL"#. This volume is
#(45.5 color(red)(cancel(color(black)("mL"))))/(10.0 color(red)(cancel(color(black)("mL")))) = color(blue)(4.55)#
smaller than what you'd need if the acid solution had the same molarity as the sodium hydroxide solution. This can only mean that the acid solution is #color(blue)(4.55)# times more concentrated than the sodium hydroxide solution.

Consequently, you have

#c_("HA") = color(blue)(4.55) * "0.200 M" = color(green)(|bar(ul(color(white)(a/a)color(black)("0.910 M")color(white)(a/a)|)))#
Therefore, you can say for a fact that #"10.0 mL"# of #"0.910 M"# monoprotic acid solution contains the same number of moles of solute as #"45.5 mL"# of #"0.200 M"# sodium hydroxide solution.
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Answer 2

The concentration of the acid is 0.091 M.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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