If it takes 25.00 ml of 0.0500 M HCL to neutralize 15.00 ml of NaOH solution, what is the concentration of the NaOH solution

Question

If it takes 25.00 ml of 0.0500 M HCL to neutralize 15.00 ml of NaOH solution, what is the concentration of the NaOH solution?

Answer 1

Hi Nykisha,

 

HCl is a strong acid and NaOH is a strong base, so we know that they will fully react with one another.

 

The first step is to write out a balanced chemical equation for this reaction:

HCl dissociates into H⁺ and Cl^- and NaOH dissociates into Na⁺ and OH^-.  This means what we have in solution is:

H⁺ + Cl^- + Na⁺ + OH^-

The positive H⁺ will be attracted to the negative OH^- to form H₂O, and the positive Na⁺ will be attracted to the negative Cl^- to form NaCl.

This gives us the reaction equation:

HCl + NaOH ⇔ NaCl + H₂O

The products and reactants balance out (the number of each atom is the same on the left hand and right hand side) so no reaction coefficients are needed.

 

Based on this reaction equation, we need 1 mol of HCl to react with each mole of NaOH.

 

The question tells us that it takes 25 mL of 0.0500 M HCl to neutralize all of the NaOH.  We need to calculate how many moles of HCl that is.

First, we convert 25 mL to Liters: 25 mL * 1 L/1000 mL = 0.025L.

M (molarity) = moles per liter, so to determine the number of moles we multiply the molar concentration (M) of HCl by the volume in liters:

0.0500 moles/L * .025L = 0.00125 moles.

 

Since our reaction equation above tells us that we use 1 mole of HCl for each 1 mole NaOH, and we know we used 0.00125 of HCl, we know we have 0.00125 moles of NaOH in the solution.

 

Now that we know the number of moles that we have, we only need to divide that by the volume to get the molar concentration (remember, molar concentration (M) = moles/liter).

The question says we have 15 mL of NaOH solution.  15 mL * 1L/1000mL = 0.015L

0.00125 moles NaOH/0.015L = 0.083 mol/L or 0.083M.