HELP ME, this is almost due and I've been busy!

What is the percentage by mass of silicon (si) in iron aluminum silicate (fe3al2(sio4)3)?

8) a mixture of he, ne and ar has a pressure of 7.85 atm. if the ne has a mole fraction of 0.47 and 8) ar has a mole fraction of 0.23, what is the pressure of he? a) 4.2 atm b) 3.7 atm c) 5.5 atm d) 2.4 atm e) 1.8 atm

How does concentration affect reaction rate