Which of the following has the longest half-life? a. 0-19
b. H-3
c. Zn-71
d. Rb-85

b. H-3

Explanation:

The half life of the following isotopes is given as;

a. 0-19

26.88 seconds

b. H-3

12 years

c. Zn-71

2.4 minutes

d. Rb-85

This is a stable isotope. It does not decomposes.

Comparing the half lives, the isotope with the longest half life is Hydrogen - 3. With half life of 12 years.

the transfer of heat by electromagnetic radiation is called thermal radiation . it is usually carried out by electromagnetic waves in an energy range just below the visible spectrum, which is the infrared range.

so the answer would be radiation.

: )

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