What is the percent yield if the actual yield is 1.5g and the theoretical yield is 4.5g?

Which is the layer underground where all empty spaces are filled with a combination of air and water ?

In an exothermic reaction the bonding energy of the product is: less than the reactants same as the reactants greater than the reactants dependent upon the presence of a catalyst

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?