General Chemistry, Kind of Related to Stoichiometry, please help! really want to learn and understand this problem

Question

This is a General Chemistry Question:

A reaction happens with 75 grams of acetic acid (C2O2H4) and an unknown metal, resulting in hydrogen gas and a solid metal with a mass of 113.4 g. What is the unknown metal?

Btw this was a question that I attempted but I'm stuck on a step where im getting that the unknown metal is 43.4 grams but Idk what the metal is since I need the answer to be in g/mol to find on the periodic table

Answer 1

Hello, Plain,

As per the comments, there are a few missing pieces that prevent me from having a confident solution. I'll share my thinking process based on a few assumptions, and perhaps you can piece together a satisfactory answer. Unfortunately, there isn't enough room in the reply box to fit my spreadsheet calculations. Sorry.

My assumptions are that the mystery metal is divalent and the metal acetate that is formed is not soluble, therefore the "precipitate." The other valid assumption would be that the metal is a monovalent, but I didn't arrive at a particularly satisfying molar mass, and therefore metal ID, based on that assumption.

The details are in the table. I calculated the moles acetic acid and assumed all were consumed in making the precipitate. If the metal is divalent, I set up a balanced equation. (M = divalent Mystery Metal)

1M + 2CH3O2H = 1M(CH3O2)2 + H2

The equation tells us that we get 1/2 mole of metal acetate for every mole acetic acid. That allows us to calculate the moles of precipitate since we have 1.25 moles of acetic acid. Since we know it's mass, we can derive it's molar mass. By subtracting out the mass of the acetate ion in the precipitate, we are left with the mass of metal. The moles of metal consumed is 1/2 of the moles of acetic acid used. The mass of the metal in the precipitate is then divided by the moles of metal to yield g/mole, the molar mass of the unknown metal. I got 61.5 g/mole. The closest I could find on the periodic table is copper, at 63.5 g/mole. Not very close, but the best I could do.

Bob