Answer:
isotopes
Atoms with the same number of protons but different numbers of neutrons are called isotopes. Because the number of neutrons can vary for a given element, the mass numbers of different atoms of an element may also vary. For example, some helium atoms have three neutrons instead of two (these are called isotopes and are discussed in detail later on)
Explanation:
Data:
Arsenic Molar Mass = 74,9216 ≈ 75 u (<span>atomic mass unit)</span>
Solving:
1 mole of arsenic → 75g ------------ 6,02*10²³ molecules
..................................X -------------- 1 molecule
6,02*10²³X = 75

The volume of a 6.67 m nacl solution
that contains 3.12 mol nacl is 0.468.
You just need to follow this formula:
C = n / V
So, it will be
V = n / C
<span> = 3.12 / 6.67 moles / Liter </span>
<span> = 0.468 L</span>