A titration to standardize a HCl solution was performed by taking 50.0ml hydrochloric acid in a flask with a few drops of phenolphthalein indicator. The burette was filled with 0.15 molar NaOH. The initial reading of the burette was 0.50ml and the final reading was 30.5ml. What is the concentration of the solution?
volume NaOH = 30.5-0.50 = 30.0
mols NaOH = M x L = ?
mols HCl = mols NaOH since 1 mol NaOH - 1 mol HCl in the titration.
Then M HCl = mols HCl/L HCl.
To find the concentration of the hydrochloric acid (HCl) solution, we need to use the concept of stoichiometry, where we compare the balanced equation of the reaction between HCl and NaOH.
The balanced chemical equation for the neutralization reaction between HCl and NaOH is:
HCl + NaOH -> NaCl + H2O
From the equation, we can see that the ratio between HCl and NaOH is 1:1. This means that if we know the amount of NaOH used, we can deduce the amount of HCl reacted.
Given information:
Volume of NaOH used = Final reading - Initial reading = 30.5 ml - 0.50 ml = 30 ml
(mL stands for milliliters)
Now, we need to convert the volume of NaOH used to moles. To do this, we need to multiply the volume (in liters) by the molarity (concentration) of NaOH.
Molarity (concentration) of NaOH = 0.15 moles/L
Converting milliliters to liters:
30 ml * (1 L/1000 ml) = 0.030 L
Now, we can calculate the number of moles of NaOH used:
moles of NaOH = volume of NaOH (in L) * molarity of NaOH
= 0.030 L * 0.15 moles/L
= 0.0045 moles
Since the stoichiometry of the balanced equation is 1:1 between HCl and NaOH, the number of moles of HCl will also be 0.0045 moles.
Finally, we need to calculate the concentration of the HCl solution. We know the volume of HCl used is 50.0 ml (0.050 L).
Concentration (molarity) of HCl = moles of HCl / volume of HCl (in L)
= 0.0045 moles / 0.050 L
= 0.09 moles/L
Therefore, the concentration of the HCl solution is 0.09 moles/L (or 0.09 M).