Question

Hydrofluoric acid, HF(aq), cannot be stored in glass bottles because compounds called silicates in the glass are attacked by the acid. Sodium silicate, Na2SiO3, for example reacts as follows: Na2SiO3(s) + 8 HF(aq) \rightarrow → H2SiF6(aq) + 2 NaF(aq) + 3 H2O(l) (balanced) If a glass container held 25.0 mL of a 0.100 M HF(aq) how many grams of the glass (Na2SiO3(s)) would be dissolved by the acid?

Answer 1

lets calculate the mol of HF
volume , V = 25.0 mL
= 2.5*10^-2 L


use:
number of mol,
n = Molarity * Volume
= 0.1*0.025
= 2.5*10^-3 mol
According to balanced equation
mol of Na2SiO3 reacted = (1/8)* moles of HF
= (1/8)*2.5*10^-3
= 3.125*10^-4 mol
This is number of moles of Na2SiO3

Molar mass of Na2SiO3,
MM = 2*MM(Na) + 1*MM(Si) + 3*MM(O)
= 2*22.99 + 1*28.09 + 3*16.0
= 122.07 g/mol

use:
mass of Na2SiO3,
m = number of mol * molar mass
= 3.125*10^-4 mol * 122.07 g/mol
= 3.815*10^-2 g
Answer: 3.81*10^-2 g