Question

A metal (M) forms a compound with the formula MC13• Ifthe com­ pound contains 65.57% Cl by mass, what is the identity ofthe metal?

Answer 1

Answer: The metal is iron.

Step-by-step explanation:

To calculate the mass percent of element in a given compound, we use the formula:-

Mass of
`MCl_3=1* x+3* 35.5=x+106.5g/mol`

Mass of chlorine =
`3* 35.5=106.5g/mol`

`\text{Mass percent of chlorine}=(106.5)/(x+106.5)* 100`

Given :
`\text{Mass percent of chlorine}=65.57\%`

Equating the two equations :

`(106.5)/(x+106.5)* 100=65.57\%`

`x=56g/mol`

Thus the atomic mass of metal is 56g/mol and the element is iron.

Answer 2

Answer : The identity of the metal is, iron (Fe).

Explanation :

As we are given that:

65.57 % Cl by mass means that 65.57 gram of chlorine present in 100 grams of compound.

Mass of compound = 100 g

Mass of chlorine = 65.57 g

Mass of metal = 100 - 65.57 = 34.43 g

First we have to calculate the moles of chlorine.

`\text{Moles of }Cl=\frac{\text{Mass of }Cl}{\text{Molar mass of }Cl}=(65.57g)/(35.5g/mole)=1.847mole`

The given formula of compound is,
`MCl_3`

The ratio of M : Cl = 1 : 3

Now we have to calculate the moles of metal.

As, 3 moles of Cl combine with 1 mole of metal

So, 1.847 mole of Cl combine with
`(1.847)/(3)=0.6157` mole of metal

Now we have to calculate the molar mass of metal.

`\text{Molar mass of metal}=\frac{\text{Given mass of metal}}{\text{Moles of metal}}=(34.43g)/(0.6157mole)=55.92g/mole`

The molar mass of metal is 55.92 g/mole. From this we conclude that the metal is iron (Fe). So, the formula will be,
`FeCl_3`

Hence, the identity of the metal is, iron (Fe).