If the half-life of substance Z is 2.5 years, how long would it take for 48 grams of substance Z to decay such that only 3
grams remain?

It takes 10 years for the substance z to decay from 48g to 3g

Half life of z = 2.5 years

Final amount of Z = 3 g

Initial amount of Z = 48 g

According to the question, it takes 2.5 years for substance Z to reduce to half.

So,

In 2.5 years, the amount of z = 48/2 = 24 grams

In next 2.5 years, the amount of z = 24/2=12g

In next 2.5 years, the amount of z = 12/2=6g

In next 2.5 years, the amount of z = 6/2=3g

To reduce the amount from 48g to 3g, total years = 2.5 + 2.5 + 2.5 + 2.5

= 10 years

Therefore, it takes 10 years for the substance z to decay from 48g to 3g

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

if you need further assistance, let me know: )

~ trueboss72