Question

Sulfur forms the chlorides ${S_2}C{l_2}$ and $SC{l_2}$. The equivalent mass of sulfur in $SC{l_2}$ is $16\;{g {\left/
A) {\vphantom {g {mol}}} \right.
 } {mol}}$. Therefore, the equivalent mass of sulfur in ${S_2}C{l_2}$ is:
$32\;{g {\left/
  {\vphantom {g {mol}}} \right.
 } {mol}}$
B) $16\;{g {\left/
 {\vphantom {g {mol}}} \right.
 } {mol}}$
C) $64\;{g {\left/
 {\vphantom {g {mol}}} \right.
 } {mol}}$
D) $8\;{g {\left/
 {\vphantom {g {mol}}} \right.
 } {mol}}$

Answer 1

Hint: It is known that the equivalent mass depends on the molar mass and valence or the oxidation state of the element in the given compound. It is also known as gram equivalent.

Complete answer:
We can relate the equivalent mass of an element in chlorides to how much of it would combine with $35.5{\rm{ g}}$ of chlorine or simply one mole of chlorine.

Let’s have a look at the given chemical formula of the first chloride which is $SC{l_2}$. In one formula unit, there are one sulfur atom and two chlorine atoms. We can infer from this that two moles of chlorine are combined with one mole of sulfur. In other words, half a mole of sulfur is required to combine with one mole of chlorine.

We also know that the molar mass of sulfur is $32\;{g {\left/
 {\vphantom {g {mol}}} \right.
 } {mol}}$. So, equivalent mass of sulfur in $SC{l_2}$ would equal to half of its molar mass which is$16\;{g {\left/
 {\vphantom {g {mol}}} \right.
 } {mol}}$.

Now, let’s have a look at the given chemical formula of the second chloride which is ${S_2}C{l_2}$. In one formula unit, there are two sulfur atoms and two chlorine atoms. We can infer from this that two moles of chlorine are combined with two moles of sulfur. In other words, one mole of sulfur is required to combine with one mole of chlorine.

We can use the molar mass of sulfur is $32\;{g {\left/
 {\vphantom {g {mol}}} \right.
 } {mol}}$ to find out the equivalent mass of sulfur in ${S_2}C{l_2}$ which would equal to its molar mass: $32\;{g {\left/
 {\vphantom {g {mol}}} \right.
 } {mol}}$
Hence, the equivalent mass of sulfur in ${S_2}C{l_2}$ is $32\;{g {\left/
 {\vphantom {g {mol}}} \right.
 } {mol}}$.

Hence the correct answer is option ‘A’.

Note: We have to keep in mind that both are chlorides but the relative number of sulfur atoms is different in both. Generally, the idea of equivalent mass to compare chemically different elements! Atoms combine with each other to form chemical compounds.