Question

A 20.38 gram sample of cobalt is heated in the presence of excess sulfur. A metal sulfide is formed with a mass of 31.47 g. Determine the empirical formula of the metal sulfide.

Answer 1

Answer: The empirical formula of the metal sulfide is
`CoBr_(2)`.

Step-by-step explanation:

Given: Mass of metal = 20.38 g

Mass of metal sulfide = 31.47 g

Moles is the mass of a substance divided by its molar mass.

So, moles of cobalt (molar mass = 59 g/mol) are as follows.

`Moles = (mass)/(molarmass)\\= (20.38 g)/(59 g/mol)\\= 0.345 mol`

Moles of bromine (molar mass = 80 g/mol) are as follows.

`Moles = ((31.47 - 20.38) g)/(80 g/mol)\\= (11.09 g)/(80 g/mol)\\= 0.138 mol`

Now, the ratio of number of moles of cobalt and number of moles of bromine are as follows.

Moles of Co : Moles of Br = 1 : 2

Hence, the empirical formula is
`CoBr_(2)`.

Thus, we can conclude that the empirical formula of the metal sulfide is
`CoBr_(2)`.