34.73%
We are given;
A mixture that contains;
We are required to determine mass percent of NaCl in the mixture;
Mass of the mixture = Mass of NaCl + Mass of NH₄Cl + Mass of SiO₂
= 0.639 g + 0.350 g + 0.851 g
= 1.84 g
The mass % of NaCl = (Mass of NaCl ÷ Mass of the mixture) 100
= (0.639 g ÷ 1.84 g) × 100
= 34.73%
Therefore, the mass % of NaCl in the mixture is 34.73%