<u>Answer:</u> The mass percent of hydrogen in methyl acetate is 8 %
<u>Explanation:</u>
The given chemical formula of methyl acetate is 
To calculate the mass percentage of hydrogen in methyl acetate, we use the equation:

Mass of hydrogen = (6 × 1) = 6 g
Mass of methyl acetate = [(3 × 12) + (6 × 1) + (2 × 16)] = 74 g
Putting values in above equation, we get:

Hence, the mass percent of hydrogen in methyl acetate is 8 %
Answer: cycloaddition of 1,3-butadiene and allyl anion is thermally allowed.
Explanation:
Using the frontier molecular orbital approach, we consider if the symmetry of the LUMO of the diene (1,3-cyclobutadiene) and the HOMO of the dienophile allyl anion), match each other since the diels alder reaction is a symmetry allowed process. The symmetries of these frontier molecular orbitals match each other hence the reaction is thermally allowed. It should be notes that 4+2 cycloadditions are thermally allowed although they are slow.
By adding a lot of carbon dioxide of what is necessary could be harmful for living things, the carbon cycle is something natural, this cycle released enough carbon dioxide, as result not to damage living things so by adding more could prejudicial