Answer:
The net change in enthalpy for the formation of one mole of acrylic acid from calcium carbide, water and carbon dioxide is 523.2 kJ.
Explanation:
Step 1:
...[1]
Step 2 :
..[2]
Adding 6 × [1] and [2]:
we get :
Energy released on formation of 5 moles of acrylic acid = 2,626 kJ
Energy released on formation of 1 mole of acrylic acid:
Answer: Uranium-235.
Radioactive isotopes are used to determine the age of antique objects, including fossils.
The half-life time of the radioactive elements is what permits the process of dating.
The half-life of C-14 is too short to be useful to date too old objects.
Precambrian time is the most antique era. C-14 hal-life is about 5730 years and Precambrian time is millions or billions of years ago. Given that the hal-life of U-235 is 704 million years it is appropiate to date the fossils from the Precambrian era.
