NY Regents Chemistry Exam June 2023 Questions 82-85
In a laboratory activity, a student measures the pH values of four household liquids and distilled water, as shown in the table below. During this laboratory activity, appropriate safety equipment is used and safety procedures are followed.
82 Identify the liquid tested by the student that is most acidic.
Solution: The lower the pH value, the more acidic substance is. Lemon juice is most acidic since it has the lowest pH value.
83 State the color of bromcresol green after the indicator is added to a sample of lemon juice.
Solution: Table M on the Reference Table lists all the indicators with their pH range and color changes. The pH range for bromcresol green is 3.8–5.4 and the color change is yellow to blue. This means for a pH below 3.8, the color will be yellow. For pH above 5.4, the color of the indicator will be blue. The pH of lemon juice is 2.1, which is lower than 3.8 resulting in a yellow color.
84 Complete the equation in your answer booklet by writing the formula of the missing product in the reaction of aqueous potassium hydroxide with the vinegar, acetic acid.
Solution: KOH(aq) + HC2H3O2(aq) → KC2H3O2(aq) +H2O
85 Based on the pH value in the table, compare the concentration of hydronium ions to the concentration of hydroxide ions in the distilled water.
Solution: Distilled water has a pH of 7 which is neutral. At a neutral pH, the concentration of hydronium ions is equal to the concentration of hydroxide ions.
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