Answer:
121.61
Step-by-step explanation:
The law of definite proportion sates that all pure samples of a particular chemical compound contain similar elements combined in the same proportion by mass.
From the question above,
The pure sample contains only metal M and Fluorine F.
Ratio of the mass of M and F in the first sample = 1.38 g : 0.71 g
Total mass = 1.38+0.71 = 2.09 g
Percentage of F present in the first sample = (0.71/2.09)×100
= 33.97%
Assuming both samples are pure,
Total mass in the second sample = 358 g.
mass of fluorine = (33.97/100)×358
mass of fluorine = 121.61