Question

The percentage weight of Zn in white vitriol \[[ZnS{O_4}.7{H_2}O]\] is approximately equal to. (at mass of \[Zn = 65\], \[S = 32\], \[O = 16\] and \[H = 1\] )
A) 33.65
B) 32.56
C) 23.65
D) 22.65

Answer 1

Hint: First, we will calculate the total mass or molecular weight of white vitriol, and then we will calculate the molecular weight of \[Zn\]. After that, we will find out the total percentage of zinc present by the percentage calculating formula.

Formula used:
After the calculation of total molecular weight of white vitriol, the percentage of zinc can be found out by:
\[\dfrac{{Weight\,of\,Zn}}{{molecular\,weight\,of\,white\,vitriol}} \times 100\]

Complete Step by Step Solution:
It is given that \[Zn = 65\], \[S = 32\], \[O = 16\], \[H = 1\]
Therefore, the molecular weight of white vitriol would be;
\[ZnS{O_4}.7{H_2}O = 65 + 32 + (4 \times 16) + 7(2 \times 1 + 16) = 287g\]
The weight of zinc in white vitriol is equal to 65g
So, the percentage weight of Zn can be calculated by;
\[\dfrac{{Weight\,of\,Zn}}{{Molecular\,weight\,of\,white\,vitriol}} \times 100\]
\[ = \dfrac{{65}}{{287}} \times 100\]
\[ = 22.65\% \]
Hence, option D is the correct answer

Note: White vitriol is another name for zinc sulphate. It occurs as a water-soluble substance that is clear and crystalline in form. It is prepared by heating the ore of zinc sulphide ore in the air, dissolving them, and recrystallizing the sulphate that is present. It occurs naturally as mineral goslarite. It is prepared by the reaction of zinc in the presence of sulphuric acid. White vitriol also offers a wide variety of uses such as:
1) It is used for the synthesis of various pharmaceutical drugs.
2) It is used widely for the manufacturing of cosmetics and oral care products.
3) It is used as an adhesive and a binding agent.
4) Used for the synthesis of antimicrobial drugs and anti-plaque agents.