You look at the atomic mass.. The number of neutrons is different for different individual atoms of the same element, each atom is also known an isotope. Looking at a periodic table, the atomic mass listed is the average atomic mass for all isotopes of that element found in nature.
Answer: It is element nitrogen. It has an atomic number of 7 and the valence electron is 5. It needs 3 electrons to complete its octet state. That's why sometimes it has the oxidation number of -3 in ammonia.
Answer: There are 0.0637 moles present in 85.0 mL of 0.750 M KOH.
Explanation:
Given: Volume = 85.0 mL (1 mL = 0.001 L) = 0.085 L
Molarity = 0.750 M
It is known that molarity is the number of moles of solute present in liter of a solution.
Therefore, moles present in given solution are calculated as follows.

Thus, we can conclude that there are 0.0637 moles present in 85.0 mL of 0.750 M KOH.
Answer:
B. 17.0.
Explanation:
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In this case, considering that based on the atomic mass of the carbon atom, which means that 1 mole of carbon weights 12.01 grams, we can set up the following proportional factor to compute the moles of carbon in 200.0 grams:

Thus, the answer would be B. 17.0.
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