The correct is this because they said
Near the coasts and Great Lakes.
13.4 billion years is 3 times of the half-life, 4.47 billion years. So the Uranium-238 will go through three times of half decay. So the remain percentage will be 50%*50%*50%=12.5%.
Answer:
A
Explanation:
because it loses 2 electrons
Answer: There are 0.000043 moles of melatonin.
Explanation:
According to avogadro's law, 1 mole of every substance occupies 22.4 L at STP and contains avogadro's number
of particles.
To calculate the moles, we use the equation:

given mass = 10 mg = 0.01 g
molar mass of
= 232.28 g
Thus there are 0.000043 moles of melatonin