Determine the Molarity of a 125 mL NaOH solution if upon titration with 5.5 mL of an 2.5 M HCl solution, the end point of the titration was reached

Write the equation and balance it.

HCl + NaOH ==> NaCl + H2O

1. moles HCl used = M x L = ??
2. Using the coefficients in the balanced equation, convert moles HCl to moles NaOH.
Since everything is a 1:1 ratio, that means moles NaOH = moles HCl.
3. Then M NaOH = moles NaOH/L NaOH and solve for M.

To determine the molarity of the NaOH solution, we need to use the concept of stoichiometry and the equation balanced equation between NaOH and HCl.

The balanced equation for the reaction between NaOH and HCl is:

NaOH + HCl -> NaCl + H2O

From the balanced equation, we can see that the stoichiometric ratio between NaOH and HCl is 1:1. This means that for every 1 mole of NaOH, we need 1 mole of HCl to react completely.

Given:
- Volume of NaOH solution = 125 mL
- Volume of HCl solution used = 5.5 mL
- Molarity of HCl solution = 2.5 M

First, we need to find the number of moles of HCl used in the titration. To do this, we can use the formula:

moles of HCl = Molarity of HCl × volume of HCl solution (in liters)

Converting the volume of HCl solution to liters:

5.5 mL = 5.5/1000 L = 0.0055 L

Calculating the moles of HCl used:

moles of HCl = 2.5 M × 0.0055 L = 0.01375 moles

Since the balanced equation shows a 1:1 ratio between NaOH and HCl, the number of moles of NaOH in the solution is also 0.01375 moles.

Now, to find the molarity of the NaOH solution, we can use the formula:

Molarity of NaOH = moles of NaOH / volume of NaOH solution (in liters)

Converting the volume of NaOH solution to liters:

125 mL = 125/1000 L = 0.125 L

Calculating the molarity of NaOH:

Molarity of NaOH = 0.01375 moles / 0.125 L

Molarity of NaOH = 0.11 M

Therefore, the molarity of the 125 mL NaOH solution is approximately 0.11 M.