What is the fraction remaining of a sample that is 5 half lives old?

The fraction remaining of a sample that is 5 half lives old is 0.03125.

Explanation:

It is known that the decay of a radioactive isotope isotope obeys first order kinetics.Half-life time is the time needed for the reactants to be in its half concentration.If reactant has initial concentration [A₀], after half-life time its concentration will be ([A₀]/2).Also, it is clear that in first order decay the half-life time is independent of the initial concentration.Suppose the initial concentration of the sample is 1:

So, it will decay as:

1.0 → (first half life) 0.5 → (second half-life) 0.25 → (third half-life) 0.125 → (fourth half-life) 0.0625 → (fifth half-life) 0.03125.

So, the rraction remaining of a sample that is 5 half lives old is 0.03125.

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.

The product formed when bao and h2o  react together is                        ba(oh)2that is  bao + h2o = ba(oh)21 mole of    bao    react  1 mole of h2o  to    form  1 mole  of ba(oh)2