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5.25 g NaF  

Step-by-step explanation:

We know we will need a balanced equation with masses and molar masses, so let’s gather all the information in one place.  

M_r:           41.99

               Na₂SiO₃ + 8HF ⟶ H₂SiF₆ + 2 NaF + 3H₂O

n/mol:                         8  

(1) Calculate the moles of NaF

The molar ratio is 2 mol NaF/8 mol HF.

Moles of F = 0.500 mol HF × (2 mol Na₂SiO₃/8 mol HF)

Moles of Na₂SiO₃ = 0.125 mol Na₂SiO₃

(2) Calculate the mass of NaF

Mass of NaF = 0.125 mol NaF × (41.99 g Na₂SiO₃/1 mol Na₂SiO₃)

Mass of NaF = 5.25 g NaF

in the given question, the partial pressure is calculated by using the ideal gas equation, that is, pv = nrt

here, p is pressure, v is volume = 25 l, n is number of moles = 0.0104 moles, r is gas constant = -0.0821 l.atm / mol.k

t is temperature = 273 k

p = nrt / v

p = (0.0104 mol × 0.0821 l.atm / mol.k × 273 k) / 25 l

= 0.0093 atm