Why might someone who lives where freshwater is plentiful worry about water shortages elsewhere?

If 34.2 grams of lithium react with excess water, how many liters of hydrogen gas can be produced at 299 kelvin and 1.21 atmospheres? 2 li (s) + 2 h2o (l) yields 2 lioh (aq) + h2 (g)

Find the number of grams of hcl needed to react completely with .50 moles of magnesium.

What best discribes the relationship between wavelength and frequency in a electromagnetic wave