What's the limitation to do enthalpy of combustion of alcohols?

Of the groups of elements below, which are most likely to gain electrons to become anions? a. alkali metal b. boron group c. halogen d. transition metal

About 3% of the water on earth is freshest. only about 40% of that freshwater is available for human use. why is so much freshwater unavailable for human use?

What is the percent by mass of magnesium sulfate in mgso4.7h2o