It’s easy, if the PH of any acidic solution = -Log[H+], where [H+] is hydrogen ion concentration, multiply each term by (-1) then raise each term as a power to (10), so it will become like this:-
[H+] = 10^(-PH)
Answer:
Option E, Half life = 
Explanation:
For a first order reaction, rate constant and half-life is related as:

Where,
= Half life
k = Rate constant
Rate constant given = 


So, the correct option is option E.
Answer
2.1 x 10 ^23
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Yes, anything with carbonate, hydrogen carbonate (bicarbonate) at the end is a carbonate.
Examples:NaHCO3 (Sodium hydrogen carbonate or Sodium bicarbonate)Na2CO3 (Sodium carbonate)
6g of hydrogen gas is my answer. I'm sorry if I'm wrong.