[trinhn812]

An ionic compound MX3 is prepared according to the following unbalanced chemical equation.
M + X2 → MX3
A 0.105-g sample of X2 contains 8.92e20 molecules.  The compound MX3 consists of 54.57% X by mass. 
What are the identities of M and X, and what is the correct name for MX3?








The balance equation is 2M + 3(X2) --> 2(MX3)

So i divided 8.92e20 molecules with avogadros number to get .00148 mol.
.105g/.00148mol gives me 70.87g/mol.
Is this right? Did i need to balance the equation? And I'm unsure how to find the identity of M.

[ARGOS++]

Dear Trinhn812;

Well done! (- till now)   ─   Full Steam ahead!

If the Molecular Weight (MW) of X₂ is 70.88g/mole, what is the Atom Weight (AW) of only one X?
Now you have identified your X. ( Use the Periodic Table!)

If three of the X’s corresponds to 54.75% of the whole mass, only 45.25% is left to your M!
Conclusion:  AW of M =  (3 * AW_X) / 54.75% * 45.25%
(Now you have also identified your M!)

Could this be of help to you?

Good Luck!
                    ARGOS⁺⁺