Solution:
Alcohol prepared by the distillation of wood is Methyl alcohol. It is also called wood spirit.

Solution:
Lemons, oranges, limes, and other citrus fruits naturally possess high concentrations of citric acid. The juice of the lemon is about 5% to 6% citric acid, which gives lemons a sour taste. In fact, Citric acid was first isolated in 1784 by the chemist Carl Wilhelm Scheele, who crystallized it from lemon juice.

Solution:
Fluorine is the most electronegative element and also the most reactive non-metal.

Solution:
Urea is a nitrogenous fertilizer.

Solution:
The mass percentage of carbon in carbon dioxide is 27.3 %.

Solution:
Carbon footprint can be reduced by recycling waste materials, using energy efficient appliances and commuting by public transport.

Solution:
Biogas is primarily composed of methane gas, carbon dioxide, and trace amounts of nitrogen, hydrogen, and carbon monoxide.