Photo AI
Gaseous HCl was bubbled into water and two solutions, X and Y - HSC - SSCE Chemistry - Question 34 - 2021 - Paper 1
Question 34
Gaseous HCl was bubbled into water and two solutions, X and Y. Solutions X and Y contain the same type of ions. The pH of each was monitored over time and recorded i... show full transcript
Worked Solution & Example Answer:Gaseous HCl was bubbled into water and two solutions, X and Y - HSC - SSCE Chemistry - Question 34 - 2021 - Paper 1
Step 1
At t0, the pH of water is 7. X and Y have pH 4.9 so are acidic.
Answer
At t0, the pH of water is neutral at 7, indicating that it has a balance of hydronium ions, H₃O⁺, and hydroxide ions, OH⁻. The lower pH of solutions X and Y, which is 4.9, shows that they are acidic due to a higher concentration of H₃O⁺ ions compared to water. Acidic solutions typically have pH values below 7.
Step 2
At t1, the pH of water is dropping rapidly due to production of H₃O⁺.
Answer
At t1, the addition of HCl gas causes the pH of water to drop as it produces hydronium ions: This reaction shows that HCl donates a proton to water, increasing the concentration of H₃O⁺ and thus lowering the pH. Solutions X and Y have also dropped in pH, indicating they react similarly by producing more H₃O⁺ when HCl is added.
Step 3
At t2, the pH of X and Y have begun to decrease, but the pH of X is lower.
Answer
At t2, the pH of solutions X and Y continues to decrease but remains lower for solution X. This is likely due to the initial conditions of the solutions, where solution X was less concentrated and thus had fewer buffering capacities than solution Y. The decreasing pH in X indicates that the concentration of H₃O⁺ ions is higher in comparison to Y, which happens as the buffer system in Y is more effective in minimizing changes in pH.