Question

A sample of an unknown pure metal(M) with a mass of 0.512g is reacted with excess HCl(aq) by the following unbalanced reaction:

M(s) + HCl(aq)→MCl2(aq) + H2(g)
a. Balance the above reaction.
b. If the 0.512g is completely consumed and converted into MCl2 (aq) and then found to weigh 1.067g, what is the molar mass and identity of the metal(M)?

Answer 1

The balanced chemical reaction is M + 2HCl → MCl2 + H2, and by comparing the mass of MCl2 produced to the mass of the metal reacted, one can determine the molar mass of the metal.

Step-by-step explanation:

To answer the student's question:

1. Balance the reaction: The balanced reaction is M(s) + 2HCl(aq) → MCl2(aq) + H2(g).
2. Determine the molar mass and identity of the metal (M): We use the mass of the metal and the mass of the metal chloride to find the molar mass. The difference between the mass of MCl2 and M is the mass of the Cl, which is 1.067g - 0.512g = 0.555g. Since there are two moles of Cl in MCl2, we divide the mass of Cl by its molar mass (35.45 g/mol for Cl) to get the moles of Cl, then multiply by 2 to get the moles of MCl2, and finally divide the original mass of M by the moles of MCl2 to find the molar mass of M.