NY Regents Chemistry Exam Jan 2023
The table below lists the hydronium ion concentration and pH values of four different solutions and distilled water. The pH value is missing for sample 2.
63. Determine the pH value of sample 2.  pH = -log[H+], we are given the concentration of hydronium ion in the table. It is 1*10^-2 for sample 2. All we need to do now is to plug in.
pH = -log(1*10^-2)
Answer: pH =2
64. Identify the ion released by the compound dissolved in sample 4 that allows the compound to be classified as an Arrhenius base. 
Arrhenius base dissociates into OH- (hydroxide ion) in water
Answer: OH- ion
65. State how many times greater the hydronium ion concentration is in sample 4 than it is in sample 5. 
Hydronium ion concentration is sample 4 is 1*10^-12 and in sample 5, it is 1*10^-13. The difference is the power of 10 (if we divide sample 4 by sample 5).
Answer: 10 times greater