The half life of a substance is the time taken by a radioactive substance to decay by half its original mass. In this case, the half life of Potassium-40 is 1.3 billion years.
Original mass of Potassium-40 = 12 g (100%)
New mass after the decay = 3 g ( 25 %, since 75% was replaced by argon)
New mass = Original mass × (1/2)^n ; where n is the number of half lives.
3 = 12 × (1/2)^n
(1/2)^n = 1/4
n = 2
Therefore; the time taken will be 1.3 × 2 = 2.6 Billion years
Answer:
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Explanation:
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The reaction s that are redox reactions are
4Li(s) +O2 (g)→ 2Li2O (s)\
Mg(s) + Fe2+ (aq)→ Mg2+(aq) + Fe(s)
<h3>Explanation</h3>
A redox reaction involve both oxidation and reduction. During redox reaction there is change in oxidation states. For example in
4Li +O2 →2Li2O Li is oxidized while O is reduced
in Mg +Fe2+ → Mg2+ +Fe Mg is oxidized since it move from oxidation state 0 to 2+ while Fe2+ is reduced since it move from oxidation state of 2+ to 0
