Suppose 128 radioactive atoms have a half-life of 15 seconds. Approximately how many radioactive atoms will be left after 60 seconds

8 electrons

Explanation:

Number of atoms = 128

Half life = 15 s

After each half life, the number of atoms reduces by half. So we need to determine how many half lives are in 60s.

Number of half lives = 60s / 15s = 4

After the first life;

Number of electrons left = 128 / 2 = 64

After the second life;

Number of electrons left = 64 / 2 = 32

After the third half life;

Number of electrons left = 32 / 2 = 16

After the fourth half life;

Number of electrons left = 16 / 2 = 8

"hydrogen bonding is the attraction of h atoms in the water molecule (slight + charge) to o atoms in a neighboring water molecule (slight - charge); it is a weak interatomic force. but it is still strong enough to the water molecules "stick" together."

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol