I need help with question 5?

Carbon dioxide plays an important role in the health of our atmosphere as it is a greenhouse gas, which means that it traps heat in our atmosphere. Because of this, Alena decides to do a study on carbon dioxide. First, Alena obtains dry ice, which is solid carbon dioxide and makes some observations about it. She notices that the dry ice is a white, brittle solid that is very cold. It is immediately sublimating as she works with it. She tests the conductivity of the solid, and there is no conductivity. However, she does realize it is soluble in water and in heptanes (a non-polar organic solvent). 1. Explain why CO2 is soluble in both water and heptanes. Alena needs to create some carbon dioxide gas. She sublimates some dry ice into a closed round-bottom flask. 2. The density of solid CO2 is 1.562g/mL. The unit cell edge length is 5.620A. CO2 crystalizes in a cubic formation. Based on this information, what is the most likely cubic structure that CO2 crystalizes in? 3. What would be the radius of the CO2 molecule in this structure? 4. Why is this value not the same as the C=O bond length for CO2(1.16A) ? 5. The vapor pressure of dry ice at 25C is 56.5atm. What would the vapor pressure be at 25C ? Alena is aware that she needs to make sure there is no air in her system or else any math she does may have error. She considers two methods for this: a. Pumping the air out with a vacuum pump first before sublimating, or b. Using a cap with small pin holes to push out the air as the sublimation occurs, thus trapping only the carbon dioxide. Which method would you recommend that she use? Use the concepts from these modules to defend your answer. 7. Alena does one trial where she accidentally forgot to switch to the cap with pin holes. She notices that the dry ice starts to melt and form a liquid then immediately evaporates into a gas. Use the concepts from these modules to explain what happened