What is the mass, in grams, of a sample of 6.98 × 10^24 atoms of magnesium (mg)?

The number of moles in a substance indicates the amount of the substance that contains the same number of particles as 12 g of the Carbon-12 isotope [or equivalent to 6.02 × 10²³ (which is used as a standard in the world of moles).

Now,

          if     6.02 × 10²³ atoms are found in 1 mole of Mg
   then let  6.98 × 10²⁴ atoms are found in     x

⇒     x  =    (6.98 × 10²⁴)  ÷  (6.02 × 10²³)
            =  11.595 mol

Also, 
    Mass = Mole  ×  Molar Mass

∴ Mass of Mg = 11.595 mol  ×  24 g / mol
                       = 278.27 g 

The mass of a sample of 6.98 × 10²⁴ atoms of magnesium (Mg) would contains   278.27 g    

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 

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