If a chemist titrates 120.0 mL of NaOH with a 5.0 M solution of HCl and requires 56.0 mL of the acid to reach the endpoint, what is the concentration of the NaOH?
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To find the concentration of NaOH, we can use the concept of molarity and the stoichiometry of the reaction between NaOH and HCl. Here's how you can calculate the concentration of NaOH:
Step 1: Write down the balanced chemical equation for the reaction between NaOH and HCl:
NaOH + HCl → NaCl + H2O
Step 2: Determine the stoichiometry of the reaction.
From the balanced equation, we can see that 1 mole of NaOH reacts with 1 mole of HCl.
Step 3: Calculate the number of moles of HCl used in the titration.
In this case, the volume of HCl used is 56.0 mL, and its concentration is 5.0 M. To find the number of moles of HCl, we can use the formula:
moles = volume (L) x concentration (M)
First, convert the volume of HCl used to liters:
56.0 mL = 0.0560 L
Then, calculate the number of moles of HCl:
moles of HCl = 0.0560 L x 5.0 M
Step 4: Since the stoichiometry of the reaction is 1:1 between NaOH and HCl, the number of moles of NaOH used in the reaction is also equal to the number of moles of HCl:
moles of NaOH = moles of HCl
Step 5: Calculate the concentration of NaOH.
The volume of NaOH used in the titration is given as 120.0 mL, which is equal to 0.1200 L. Now we can use the formula:
concentration (M) = moles/volume (L)
Substituting the calculated values, we have:
concentration of NaOH = moles of NaOH / volume of NaOH
concentration of NaOH = (moles of HCl / 0.1200 L)
By following these steps and substituting the appropriate values, you will be able to calculate the concentration of NaOH.