Multiply .800 moles of O2 by Avagadro's number divided by 1 mole. This will get rid of the moles on the bottom and leave you with molecules. So technically .800 times 6.02x10^23.
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.
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Answer: Temperature final = 103 °C
Explanation: To solve for final temperature we use the equation of heat:
Q= mc∆T
Next derive the equation to find final temperature
Q = mc(T final - T initial)
Q / mc = T final - T initial
Transpose T initial and change the sign so that T final will be left.
T final = Q / mc + T initial
Substitute the values:
T final = 305 J / 28.8 g x 0.128 J/(g°C)
= 305 J / 3.6864 J/°C
= 82.7 + 20.0°C
= 103 °C final temperature.
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