25.00 mL of a solution of HCL was titrated with 0.4500 M NaOH using the indicator bromthymol blue. Successice readings of the burette gave the following data: colour:
Volume of NaOH (mL)= i.) 16.35 yellow
ii.) 16.40 yellow
iii.) 16.45 green
iv.) 16.50 blue
Based on the data, the original [HCL] is...
I would average the readings of the base, then mL acid x M acid = mL base x M base. Then round to 4 significant figures.
To determine the original concentration of HCl, we can use the concept of stoichiometry and the balanced equation for the reaction between HCl and NaOH. The balanced equation is as follows:
HCl + NaOH → NaCl + H2O
In this reaction, 1 mole of HCl reacts with 1 mole of NaOH to produce 1 mole of NaCl and 1 mole of water.
To find the concentration of HCl, we need to determine the volume of NaOH required to neutralize the HCl solution.
From the given data, we can see that the color changed from yellow to green between the second and third readings. This indicates that a neutralization reaction occurred. The volume of NaOH added during this color change represents the amount needed to neutralize the HCl.
The volume of NaOH required to neutralize HCl can be determined by taking the difference between the third and second readings:
Volume of NaOH required = Third reading - Second reading = 16.45 mL - 16.40 mL = 0.05 mL
Now we can calculate the amount of NaOH used in moles by multiplying the volume (in liters) by the molarity of NaOH:
Amount of NaOH used = (Volume of NaOH required / 1000) × Molarity of NaOH
= (0.05 mL / 1000) × 0.4500 M
= 0.0000225 moles
According to the balanced equation, this amount of NaOH is equivalent to the amount of HCl present in the solution.
Therefore, the initial moles of HCl can be calculated as:
Initial moles of HCl = Amount of NaOH used = 0.0000225 moles
Since the volume of the HCl solution is given as 25.00 mL, we can convert the moles of HCl to the concentration (molarity) by dividing the moles by the volume in liters:
[HCl] = Initial moles of HCl / Volume of HCl solution (in liters)
= 0.0000225 moles / (25.00 mL / 1000)
= 0.0000225 moles / 0.025 L
= 0.900 M
Therefore, the original concentration of HCl is 0.900 M.