0.299 g of NH4Cl is dissolved in 50.0 ml then titrated against 0.205 M NaOH. Calculate the pH at the equivalent point
To calculate the pH at the equivalence point of the titration, we first need to determine the moles of NH4Cl and NaOH involved in the reaction.
Step 1: Calculate the moles of NH4Cl:
Given mass of NH4Cl = 0.299 g
Molar mass of NH4Cl = 53.49 g/mol
Moles of NH4Cl = (mass of NH4Cl) / (molar mass of NH4Cl)
Substituting the values,
Moles of NH4Cl = 0.299 g / 53.49 g/mol
Step 2: Calculate the volume of NaOH solution:
Given volume of NH4Cl solution = 50.0 mL
Volume of NaOH solution (titrant) is usually equal to the volume of the analyte, so volume of NaOH solution = 50.0 mL = 0.050 L
Step 3: Calculate the moles of NaOH:
Given concentration of NaOH = 0.205 M
Molarity (M) = moles / volume (L)
Moles of NaOH = (concentration of NaOH) x (volume of NaOH solution)
Substituting the values,
Moles of NaOH = 0.205 M x 0.050 L
Step 4: Determine the reactants and products:
NH4Cl reacts with NaOH to form NH3 (ammonia) and H2O (water). The equation is as follows:
NH4Cl + NaOH -> NH3 + H2O
Step 5: Determine the limiting reactant:
Since NH4Cl and NaOH react in a 1:1 ratio, the limiting reactant is the one with fewer moles. In this case, the limiting reactant is NH4Cl.
Step 6: Calculate the moles of excess NaOH:
Excess moles of NaOH = Moles of NaOH - Moles of NH4Cl
Step 7: Calculate the moles of NH3 produced:
Since NH4Cl and NaOH react in a 1:1 ratio, the moles of NH3 produced will be equal to the moles of NH4Cl reacted.
Step 8: Calculate the concentration of NH3:
Concentration of NH3 = (Moles of NH3) / (Volume of NaOH solution)
Step 9: Calculate the pOH at the equivalence point:
pOH = -log10 (concentration of NH3)
Step 10: Calculate the pH at the equivalence point:
pH = 14 - pOH
By following these steps, you can calculate the pH at the equivalence point of the titration.