Why is the enthalpy of formation of oxygen zero?

Someone offer some answers to this, i will give 98 coins and mark as brainliest! i will put the rest of the lab down in the comments,solutions pre-lab questions: in this lab, you will make fruit drinks with powdered drink mix. complete the pre-lab questions to get the values you need for your drink solutions. calculate the molar mass of powered fruit drink mix, made from sucrose (c12h22o11).using stoichiometry, determine the mass of powdered drink mix needed to make a 1.0 m solution of 100 ml. (hint: use molarity = to find the moles of drink mix, then convert moles to grams using a mole conversion.)what mass of powdered drink mix is needed to make a 0.5 m solution of 100 ml?