Question

Hydrofluoric acid, HF(aq), cannot be stored in glass bottles because compounds called silicates in the glass are attacked by the HF(aq). Sodium silicate (Na2SiO3), for example, reacts as follows: Na2SiO3(s)+8HF(aq)→H2SiF6(aq)+2NaF(aq)+3H2O(l)

Part A How many moles of HF are needed to react with 0.370 mol of Na2SiO3?

Part B How many grams of NaF form when 0.600 mol of HF reacts with excess Na2SiO3?

Part C How many grams of Na2SiO3 can react with 0.820 g of HF?

Answer 1

Na2SiO3(s)+8HF(aq)→H2SiF6(aq)+2NaF(aq)+3H2O(l)

A. 1 mole of Na2SIO3 react with 8 moles of HF

0.37 moles of Na2SIO3 react with = 8*0.37 =2.96 moles

B. 1 mole of Hf react with Na2SiO3 to form 2 moles of NaF

0.6 moles of HF react with Na2SiO3 to form = 2*0.6 = 1.2 moles of NaF

mass of NaF = no of moles * molar mass

                    = 1.2 *42 = 50.4 gm of NaF

C.8 moles of Hf react with 1 mole of Na2SiO3

8*18 gm of Hf react with 122 gm of Na2SiO3

0.82gm of HF react with =122*0.82/8*18 = 0.694 gm of Na2SIO3