Answer:
Incomplete precipitation of barium sulfate
Explanation:
The student has precipitated and digested the barium sulfate on his/her side. But on the addition of in the solution, the solution become cloudy. This happened because incomplete precipitation of barium sulfate by the student. When is added, there are still sulfate ions present in the solution with combines with and forms and the formation of this precipitate makes the solution cloudy.
The density of the rubber ball is calculated by the mass of the rubber ball divided by the volume of the rubber ball.
21mL-15mL=6mL which is the volume of the rubber ball
D=10g/6mL
D=1.666g/mL density of the rubber ball
What exactly is the question you are asking?
The indicator, phenolphthalein is added to the analyte as an indicator in acid–base titrations.
Phenolphthalein is a color changing indicator for acid base titrations.
Titration is a quantitative technique used to find concentration of an unknown solution(analyte ) from a solution of known concentration. which is the titrant.
Now the procedure is set up that, the titrant is in the burette and added to the analyte with known volume)in a conical flask in the presence of an indicator till the endpoint of the reaction.
This is marked by a sharp change of color to explain the point when the titrant neutralizes the analyte solution.(phenolphthalein is colorless in acidic solutions but turns pink in basic solutions).
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According to Bronsted-Lowery concept of acid and base, Acid is that substance which donated H⁺, while, Base is that substance which accepts H⁺.
Hydroiodic Acid being a strong Acid with Ka value of 3.2 × 10⁹ is when dissolved in water it donates H⁺ to water and water acts as a Base. i.e.
HI + H₂O → H₃O⁺ + I⁻
H₃O⁺ formed is the conjugate Acid of H₂O, while I⁻ is the Conjugate Base of HI.