Question

Be sure to answer all parts.

A 0.463−mol sample of a metal oxide, M₂O₃, weighs 69.4 g.

(a) How many moles of O are in the sample?



(b) How many grams of M are in the sample?



(c) Which element is represented by the symbol M? (Give the elemental symbol of that element.)

Answer 1

a)
number of mole of O atom = 3*(number of mole of M2O3)
= 3*0.463
= 1.39 mole

b)
number of mole metal = 2*(number of mole of M2O3)
= 2*0.463
= o.926 mole

atomic mass of O = 16 g/mol
molar mass of M2O3 = (given mass M2O3)/(number of mole of M2O3)
2*(atomic mass of M)+3*atomic mass of O)= 69.4/0.463
2*(atomic mass of M)+3*16= 150 g/mol
2*(atomic mass of M)+ 48 = 150 g/mol
2*(atomic mass of M) = 102 g/mol
(atomic mass of M) = 51 g/mol

mass of M in sample = (number of mole of M)*(molar mass of M)
= 0.926*51
= 47.2 g

c)
molar mass of Cr = 51.23 g/mol
so,
M represent Cr