The heaviest known isotope of hydrogen is called tritium, . it decays by beta emission, and has a half-life of 12.3 years. what fraction of a tritium sample will remain after 5.20 years?

= 3/4

Explanation:

Half life is the time taken by a radioactove element to decay by half of its original mass.

The half life of tritium is 12.3 years , therefore it would take 12.3 years for tritium to decay to a half its original mass.

Using the formula;

New mass = Initial mass × (1/2)^n ; where n is the number of half lives.

n = 5.2 years/12.3 years

  = 52/123

Therefore;

New mass = 1 × (1/2)^(52/123)

                  = 0.74599

                  = 0.75

The fraction of a tritium sample after 5.20 years will be approximately 3/4

answer: - 3.) the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

solution: - as per the rules, oxidation number of oxygen in its compounds is -2. the sum of oxidation numbers of all the elements of a molecule or compound is zero.

also, the oxidation number in elemental form is zero.

in no, the oxidation number of o is -2 so the oxidation number of n is +2 so that the sum is zero.

similarly, the oxidation number of c in co is +2 and o is -2.

on product side the oxidation number of n is 0 as it is in the elemental form() .

oxidation number of c in carbon dioxide is +4 as there are two oxygen in it and we know that each oxygen is -2.

so, oxidation number of n is changing from +2 to 0 and the oxidation number of c is changing from +2 to +4.

since nitrogen is reduced and hence no is acting as an oxidizing agent. carbon is oxidized and so co is acting as a reducing agent.

so, the right choice is number 3.)the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.