Aqueous hydrogen fluoride (hydrofluoric acid) is used to etch glass and to analyze minerals for their silicon content. Hydrogen fluoride will also react with sand (silicon dioxide). (a) Write an equation for the reaction of solid silicon dioxide with hydrofluoric acid to yield gaseous silicon tetrafluoride and liquid water. (b) The mineral fluorite (calcium fluoride) occurs extensively in Illinois. Solid calcium fluoride can also be prepared by the reaction of aqueous solutions of calcium chloride and sodium fluoride, yielding aqueous sodium chloride as the other product. Write complete and net ionic equations for this reaction.

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Explanation:

The balanced reaction equation of the reaction between SiO2 and HF is shown below;

SiO2(s) + 4HF(aq) = SiF4(g) + 2H2O(l)

b)

2NaF(aq) + CaCl2(aq) > 2NaCl(aq) + CaF2(s)

The complete ionic equation is;

2 Na^+(aq) + 2F^-(aq) + Ca^+(aq) + 2 Cl^-(aq)> 2 Na^+(aq) + 2 Cl^-(aq) + CaF2(s)

The net ionic equation;

Ca^+(aq) + 2F^-(aq) > CaF2(s)

"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"