Question

A metal, X forms 2 different chlorides. if 12.70g of chloride A and 16.30g of chloride B contain 7.10g and 10.70g of chlorine respectively, what will be the formula of the compounds?

Answer 1

Answer on Question #72239, Chemistry / Inorganic Chemistry

A metal, X forms 2 different chlorides. if 12.70g of chloride A and 16.30g of chloride B contain 7.10g and 10.70g of chlorine respectively, what will be the formula of the compounds?

Solution

The general formulas of the chlorides are $\mathrm{XCl}_n$ and $\mathrm{XCl}_m$, where $n,m$ – metal valence. Metal index is always 1, because chlorine valence is 1.

Find the mass of metal in each compound:

As it is seen there are the same masses of metal in the compounds. That means that there are the same amounts of it.

Find the amount of chlorine in the first compound ($\mathrm{XCl}_n$):

$$v_1 = \frac{7.1}{35.5} = 0.2 \text{(mole)}$$

If the formula is XCl, there is the same amount of metal in it (0.2 mole). Find its molar mass:

$M = \frac{5.6}{0.2} = 28 \text{ (g/mole)}$. It’s silicon. But silicon doesn’t form chloride SiCl. So the proposed formula is wrong.

If the formula is $\mathrm{XCl}_2$, the amount of metal X is 0.1 mole. Find its molar mass:

$M = \frac{5.6}{0.1} = 56 \text{ (g/mole)}$. It’s iron. Iron does form chloride $\mathrm{FeCl}_2$.

Let’s check our prediction using another chloride $\mathrm{XCl}_m$, remembering that the amount of metal in it is the same (0.1 mole).

Find the amount of chlorine:

$$v_2 = \frac{10.7}{35.5} = 0.3 \text{(mole)}$$

As the amount of X is 0.1 mole than the formula is $\mathrm{XCl}_3$. Iron does form chloride $\mathrm{FeCl}_3$.

Answer

$\mathrm{FeCl}_2, \mathrm{FeCl}_3$.

Answer provided by AssignmentExpert.com