The correct answer is D - When burning a log, the wood combined its components with oxygen. if you could capture the products (CO2, H2O, C, CO, etc), you would have a greater mass than what you started with, burning the log combined the log's components with oxygen in order to burn it.
#4 and #5:
To find pH given concentration of H+ or H30+
pH = - log (H+ or H30+ M)
To find pH given concentration of OH-
Since you already found the pH for this (in #4), you subtract #4's answer from 14.
14 - (pH) = pOH
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
The person above me is correct I took a test on this so it’s the right answer