C3H8 + 5O2 → 3CO2 + 4H2O

What is the mass of O2 needed to produce 31.0 moles of H2O?
(2step)

m= 1240 g O2

Explanation: We will do stoichiometry for this problem to solve for the mass of O2 in grams.

First step is to convert the moles of H2O to moles of O2 using their mole ratio.

31.0 moles H2O x 5 moles O2 / 4 moles H2O

= 38.75 moles O2

Next is to convert the moles of O2 to mass using the molar mass of O2.

38.75 moles O2 x 32 g O2 / 1 mole O2 = 1,240 g O2

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