Element x has two naturally occurring isotopes, 65x (isotopic mass 65.0234 amu, abundance 47.78%) and 67x (isotopic mass 67.1396 amu, abundance 52.22%). calculate the atomic mass of element x.

66.1285 amu

Explanation:

The atomic mass of an element is equal to the weigthed average of the atomic masses of its isotopes:

atomic mass = ∑ (relative abundance × isotopic mass)atomic mass = relative abundance of isotope ⁶⁵X × isotopic mass of isotope ⁶⁵X + relative abundance of isotope ⁶⁷X × isotopic mass of isotope ⁶⁷Xatomic mass = 47.78% × 65.0234 amu + 52.22% × 67.1396 amuatomic mass = 66.1285 amu ← answer

For cyclohexane compounds drawn in a chair conformation:   -axial bonds are vertical  -equatorial bonds are parallel to two bonds within the ring.  thus, as i assume the chair conformation is drawn:   -the x group is in an axial position, as are the five other vertical bonds.  -three axial bonds are on the top face of the ring  -the other three axial bonds are on the bottom face  the position of the second substituent on each ring carbon is equatorial.  gauche groups must be on an adjacent carbon such as carbon 6 and carbon 2, and also gauche groups are rotated by 60 degrees relative to each other.  drawing the newman projections for c1–c2 and c1–c6 aids in visualizing the groups that are gauche to the y group on c1.  click this link and watch some academic videos that may you more understand the topic