Asample of gas has an initial volume of 25 l and an initial pressure of 3.5 pa. if the pressure changes to 1.3 pa, find the new volume, assuming that the temperature remains constant.

Since you are provided with the pressure and initial volume and told a standard temperature, you should use the Combined gas law. This is (P1 V1)/ T1 = (P2 V2)/ T2 
STP is 273 k for temperature, so plug in the values. 
(3.5 Pa * 25 L)/ 273 K =1.3 Pa * X L)/ 273 K.
(this is the left side>)0.32051= 1.3 X/ 273.  Multiply both sides by 273 to get rid of it on the right, which leaves you with
87.4999 = 1.3 X. Divide both sides by 1.3 and there you go, 

67.308 L

During photosynthesis, plants transform electromagnet energy from the sun into chemical energy.

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