IMAT 2021 51 ACID BASE key concepts

Practice Question Solving
1

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Answer: A
correct me if im wrong:
Reasoning for answer is,

  1. wrong

  2. Wrong. Both nitric and sulfuric acid are strong acids and will dissociate fully in into ions.

  3. True.

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2

for 3 what do u mean by “if it was a monoprotic strong acid, pH of 2 would be correct”? wouldn’t the pH if it were monoprotic simply be -log[0.05] which is around 1.3? also for diprotic we calculate ph by multiplying the concentration by 2 as in -log[(0.05x2)], right?

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4

Thank you for your feedback. There are numerous information out there saying that a solution of H2SO4 will not completely release 2 protons at room temp and there are specific calculation methods for that but for IMAT level, I guess the approximate pH would be 1.

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6

the best way to solve this is by using log rules. so we know that pH = -log[H+], and as the first proton of H2SO4 fully dissociates we know that the ph = -log[0.05]. Now, we need to simplify 0.05 into the standard form which will give us pH = -log[5 * 10^-2 ]. This can be further simplified to:
pH = -(log[10^-2] + log[5])
pH =-log[10^-2] -log[5]
now we know that log of 10^-2 = -2
therefore
pH= -(-2) -log[5]
pH = 2 - log[5]
You should know that the log (to the base 10) of any number less than 10 will be less than 1, and any number more than 1 will be more than 0. Therefore we know that log[5] equals a number between 0 and 1. This will mean that Y’s pH, regardless of whether the second proton dissociates partially or not, will be less than 2.

I hope this helps.