Acid-Base Titration Lab Quiz

What is the main purpose of performing an acid-base titration in this experiment?

• To change the color of the solution

• To accurately measure the temperature of the solution

• To determine the molarity of an unknown acid or base solution

• To create a fizzing reaction for visual effect

In an acid-base titration, what is the role of the phenolphthalein indicator?

• It measures the pH directly by changing its own pH

• It indicates when the acid has completely dissolved

• It changes color at (or just after) the point of neutralization

• It prevents the solution from overheating

According to the lab, which piece of equipment is primarily used to measure and deliver the unknown HCl solution?

• A 100 mL graduated cylinder

• A 250 mL beaker

• A dropper pipette

• A 1 mL syringe

In the equation Ma×Va=Mb×Vb, what does Ma represent?

• The molarity of the base

• The molarity of the acid

• The mass of the acid

• The molality of the solution

The first permanent pale pink color that remains in the solution for at least ~30 seconds indicates what?

• The solution has just begun to freeze

• The endpoint of the titration

• The point where extra acid is added

• An equipment malfunction

When using a pH probe (Part B of the procedure), why is it recommended to add smaller increments of the NaOH solution as you approach pH 7?

• It prevents the solution from becoming too cold

• It reduces the chance of splashing the solution

• It allows more precise determination of the equivalence point

• It speeds up the reaction so you can finish quickly

What is the overall reaction taking place when NaOH is titrated with HCl?

• NaOH + HCl → NaCl + H2O

• NaOH + HCl → NaH + OCl

• NaOH + HCl → NaOH + HCl (no reaction)

• HCl + H2O → Cl− + H3O+

In the lab’s microtitration with phenolphthalein, which step ensures that the added base and acid mix thoroughly for an accurate endpoint?

• Leaving the solution completely still

• Heating the solution gently on a hot plate

• Gently swirling or stirring the solution after each addition of NaOH

• Using a magnetic stir bar in the HCl container

During the pH probe titration, how do you identify the equivalence point from the pH vs. volume graph?

• It is the point where pH suddenly drops to 1

• It is where pH remains exactly at 14

• It is the point with the steepest slope (near pH 7 for a strong acid-strong base)

• It is always at pH = pKa

After completing the titration and data collection, which of the following is the correct next step regarding cleanup?

• Discard all solutions in the sink without any rinsing

• Rinse the pH probe with distilled water and return it to storage solution

• Soak the pH probe in hydrochloric acid overnight

• Leave the beaker filled with leftover acid and base on the counter