construct a rough plot of ph versus volume of base for the titration of 25.0ml of 0,05M HCN with 0.075M NaOH
To construct a plot of pH versus volume of base for the titration of 25.0 mL of 0.05 M HCN with 0.075 M NaOH, we need to understand the reaction that occurs during titration and the corresponding pH changes.
The reaction between HCN (a weak acid) and NaOH (a strong base) forms water and a salt (sodium cyanide):
HCN + NaOH → H2O + NaCN
During this reaction, the HCN is partially neutralized by the NaOH, resulting in a decrease in the concentration of HCN and the formation of water. The pH of the solution will change as the reaction progresses.
To plot pH versus the volume of base added, we need to determine the pH at different stages of the titration. This can be done by calculating the moles of HCN and NaOH, and then using the stoichiometry of the reaction to determine the moles of HCN that have reacted at each point.
Here's how you can calculate the pH at different points during the titration:
1. Determine the moles of HCN initially present:
Moles of HCN = volume of HCN (in L) x molarity of HCN
= 0.025 L x 0.05 mol/L
= 0.00125 mol
2. Calculate the moles of NaOH added at each point during titration:
Moles of NaOH = volume of NaOH added (in L) x molarity of NaOH
3. Use the stoichiometry of the reaction to determine the moles of HCN neutralized by NaOH at each point.
4. Calculate the concentration of HCN at each point:
Concentration of HCN = (moles of HCN initially present - moles of HCN neutralized) / total volume of the solution (in L)
5. Determine the pOH at each point using the concentration of HCN:
pOH = -log[concentration of HCN]
6. Calculate the pH at each point using the pOH:
pH = 14 - pOH
By repeating steps 2-6 for different volumes of NaOH added, you can calculate the pH at different stages of the titration. Plotting these pH values against the corresponding volumes of NaOH added will give you a rough plot of pH versus volume of base.
Note: The exact shape of the plot will depend on the equilibrium constants and the dissociation constant of HCN.
We can't draw diagrams/structures on this board. You can find the plot you want among this group.
http://www.chemguide.co.uk/physical/acidbaseeqia/phcurves.html