Answer:

Explanation:
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In this case, since the buffer is not given, we assume it is based off ammonia, it means the ammonia-ammonium buffer, whereas the ammonia is the weak base and the ammonium ion stands for the conjugate acid. In such a way, when adding HI to the solution, the base of the buffer, NH3, reacts with the former to promote the following chemical reaction:

Because the HI is totally ionized in solution so the iodide ion becomes an spectator one.
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Answer:
The answer to your question is below
Explanation:
When we have the number of an element followed by a number, that number is the atomic mass.
Atomic mass is the number of protons plus neutrons.
Protons Neutrons
Carbon-13 6 13 - 6 = 7
Chromium-51 24 51- 24 = 27
Strontium-88 38 88 - 38 = 50
Boron-10 5 10 - 5 = 5
Lithium is a good reducing agent because it is electropositive [it rapidly gains electrons]
fluorine is good oxidizing agent electronegative [it loses electrons fastly]