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
Answer:
You should rinse your head thoroughly ASAP, don't try to blow on the chemical or anything. Its going burn, you have to let your head cool off.
Explanation:
why rinse off your hand? you're getting the fluid away fast, so I can't infect your skin that much.
Answer:
The isotope with the greatest number of protons is:
- <u>option D: Pu-239, with 94 protons</u>
Explanation:
The number of <em>protons</em> is the atomic number and is a unique number for each type of element.
You can tell the number of protons searching the element in a periodic table and reading its atomic number.
Thus, this is how you tell the number of protons or each isotope
Sample Chemical symbol Element atomic number # of protons
A Pa-238 Pa protactinium 91 91
B U-240 U uranium 92 92
C Np-238 Np neptunium 93 93
D Pu-239 Pu plutonium 94 94
Answer:
0.35 atm
Explanation:
It seems the question is incomplete. But an internet search shows me these values for the question:
" At a certain temperature the vapor pressure of pure thiophene (C₄H₄S) is measured to be 0.60 atm. Suppose a solution is prepared by mixing 137. g of thiophene and 111. g of heptane (C₇H₁₆). Calculate the partial pressure of thiophene vapor above this solution. Be sure your answer has the correct number of significant digits. Note for advanced students: you may assume the solution is ideal."
Keep in mind that if the values in your question are different, your answer will be different too. <em>However the methodology will remain the same.</em>
First we <u>calculate the moles of thiophene and heptane</u>, using their molar mass:
- 137 g thiophene ÷ 84.14 g/mol = 1.63 moles thiophene
- 111 g heptane ÷ 100 g/mol = 1.11 moles heptane
Total number of moles = 1.63 + 1.11 = 2.74 moles
The<u> mole fraction of thiophene</u> is:
Finally, the <u>partial pressure of thiophene vapor is</u>:
Partial pressure = Mole Fraction * Vapor pressure of Pure Thiophene
- Partial Pressure = 0.59 * 0.60 atm
