PLEASE SEND HELP? Im unsure of how to solve this?

When the following equation is balanced using the smallest possible integers, what is the coefficent of oxygen gas? c7h16o(g) + o2(g) → co2(g) + h2o(g) -1 -5 -8 -16 -21

Although respiratory organs vary across different organisms, they all contain respiratory surfaces that have a large surface area and are extremely thin. explain why having an extremely thin respiratory surface with a large surface area is advantageous for the process of gas exchange

Which of these is not an example of chemical weathering? a. iron-rich mineral rusting b. feldspar turning into clay c. limestone reacting with acid d. granite breaking up into sand