Question

l. A 3.41 g sample of a metallic element, M, reacts completely with 0,0158 moles of a gas, X2. to form 4.52 g of MX, What are the identities of M and X? 2. A mixture of Fezoy and Feo was found to contain 72.00% Fe by mass. What is the mass of Felo in 0.500 g of this mixture?

using the attached image answer the 2 questions show all work and all conversion factors.

Answer 1

1)

reaction :  

2 M         + X2 ------------------------> 2 MX

2mol           1 mol                            2 mol

?            0.0158 mol

moles of M needed = 2 x 0.0158 = 0.0316

mass of   M = 3.41 g

molar mass = 3.41 / 0.0316 = 108 g / mol

molar mass of M = 108 g / mol . it indicates it is silver

M = silver (Ag)

MX formed = 4.52 g

mass of X = 4.52 - 3.41 = 1.11 g

molar mass of X = 1.11 / 0.0158

molar mass of X   = 70.2 g / mol

this molar mass belongs to Cl2

so

X = Cl (chlorine)