Fossil Fuels Account for Lowest Share of U.S. Energy Consumption in More than a Century. Fossil fuels supplied about 80 percent of the energy consumed in the United States in 2017, the lowest share since 1902, according to a new report from the U.S. Department of Energy.

Actually Welcome to the concept of General organic chemistry.
1.) The formula for alkanes is Cn H2n+2
===> here n = 500, hence we get as,
C500, 2n+2 = 2(500)+2 ==> 1000+2 ==> 1002
hence the formula is ==> C500 H1002
2.) The formula for alkenes is,
CnH2n
hence, here n = 15
so we get as,
===> C15 H30
Phenolphthalein is not a good indicator to use for a titration for a solution that has a ph of 6.0 at the equivalence point because the color change of the solution at this pH level is not sharp. It changes the color of the solution to pink starting from pH 8.3 to 10. A pH level lower than 8.3 would only show a colorless solution. Thus, you would not be able to distinguish whether the solution has reached its equivalence point at pH 6.0. It is best to use this indicator for a system that is using a strong base titrated with a weak acid.
Answer:
A chemical reaction that stores energy is called an endothermic reaction. More energy might be released as products form than the energy needed to break the reactants apart. This chemical reaction will release energy. In other words, it will be an exothermic reaction.
Explanation: