Respuesta :
Mass of potassium hydrogen pthalate KHP is 0.4856 g, its molar mass is 204.22 g/mol, number of moles of KHP can be calculated as follows:
[tex]n=\frac{m}{M}[/tex]
Here, m is mass and M is molar mass, putting the values,
[tex]n=\frac{0.4856 g}{204.22 g/mol}=0.00237 mol[/tex]
This will be number of moles of NaOH at equivalent point.
Detailed calculations:
Molarity is defined as number of moles in 1 L of solution, for 250 mL of solution, molarity will be:
[tex]M=\frac{0.00237 mol}{250 \times 10^{-3}L}=0.009511 M[/tex]
For 25 mL, apply dilution law as follows:
[tex]M_{1}V_{1}=M_{2}V_{2}[/tex]
Putting the values,
[tex]0.009511\times 250=M_{2}\times 25 mL[/tex]
On rearranging,
[tex]M_{2}=\frac{0.009511\times 250}{25}=0.09511 M[/tex]
Convert molarity into number of moles,
[tex]n=M\times V=0.09511 mol/L\times 25\times 10^{-3}L=0.00237 mol[/tex]
At equivalent point, number of moles of KHP will be equal to NaOH, thus, number of moles of NaOH will be 0.00237 mol.
Calculation for molarity:
Volume of NaOH is 18.75 mL, thus, molarity can be calculated as follows:
[tex]M=\frac{n}{V}[/tex]
Putting the values,
[tex]M=\frac{0.00237 mol}{18.75\times 10^{-3}L}=0.1264 M[/tex]
Therefore, molarity of NaOH is 0.1264 M
