The reaction between zinc and hydrochloric acid is carried out as a source of hydrogen gas in the laboratory:
Zn(s) + 2 HCl(aq) ZnCl2(aq) + H2(g)
If 325 mL of hydrogen gas is collected over water at 25 °C at a
total pressure of 748 mm Hg, how many grams of Zn reacted?

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"

one negative thing it that it can kill water animals. another negative thing is it can cause the destruction of ecosystem. one way water pollution can be reduced is to conserve energy.