680 g of sodium 24 was placed in a container to decay if there is now 85 g of sodium 24 left how long has the sodium been decaying

Explanation:

The time taken for the radioactivity of a specified isotope to fall to half its original value is called half life of that radioactive material.

Half life of sodium-24 is hours.

Initial amount of sodium-24 is

In hours,the quantity falls to

In another hours,the quantity falls to

In another hours,the quantity falls to

So,it takes hours for the quantity to become .

the answer is either b or c

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.