Final answer:
To calculate the titration results, the concentration of the base is found using molarity and volume. The mass of NaOH per dm³ and the mass of NaCl formed are determined through stoichiometry and molar masses. Phenolphthalein is a suitable indicator for this titration, changing from colorless to pink at the endpoint.
Step-by-step explanation:
To answer the student's question regarding the acid-base titration calculations, we will step through each part of the question based on the neutralization reaction given:
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O
- a. The concentration of the base (NaOH) in moles per dm³ can be found by multiplying the molarity of the NaOH solution (0.100 M) by the volume required for neutrality, which is 12.6 mL, converted to dm³ (0.0126 dm³). Thus, the number of moles of NaOH is 0.100 M × 0.0126 dm³ = 0.00126 moles.
- b. To find the value of Y, which represents the grams of NaOH per dm³, we can use the molar mass of NaOH (approximately 40 g/mol) and multiply it by the concentration in moles per dm³. Hence, Y = 40 g/mol × 0.100 M = 4 grams of NaOH per dm³.
- c. Considering the stoichiometry of the reaction where 1 mole of HCl reacts with 1 mole of NaOH to form 1 mole of NaCl, the mass of NaCl formed during the reaction will be equal to the number of moles of NaOH used. With NaCl having a molar mass of approximately 58.44 g/mol, the mass of NaCl formed is 0.00126 moles × 58.44 g/mol = 0.07364 grams.
- d. A suitable indicator for this titration would be phenolphthalein, which changes from colorless to pink at the endpoint. This is because the reaction involves a strong acid (HCl) and a strong base (NaOH) which has an equivalence point at a pH of 7.00, where phenolphthalein changes color.