Question

What is the percent composition of ${{H}_{2}}S$?

Answer 1

Hint : We know that to find the molar mass of the water molecule. Then find the molar mass of hydrogen and oxygen present in the water molecule individually based on their no. of atoms in the molecule. Then to find percentage compositions divide the molar mass of hydrogen and oxygen respectively with the total molar mass of water molecules.

Complete Step By Step Answer:
Molar mass is the mass of one mole of the element or compound in grams. One mole contains Avogadro no. particles in a substance which can be atoms, molecules or ions. The percentage composition states how much percentage of the particular element is contained in the molecule of the compound formed from them.
The percentage of component present in a compound is (relative formula mass of component $\div$ relative formula mass of compound) $\cdot 100$ The relative atomic mass of $H$ (hydrogen) is $1$ ; the relative formula mass of ${{H}_{2}}$ is $2.$ The relative atomic mass of S (sulphur) is $32.$
$\therefore 2+32=34$
The compound ${{H}_{2}}S$ is known as hydrogen sulphide, relative formula mass of ${{H}_{2}}~\div ~$ relative formula mass of ${{H}_{2}}S$) $\cdot 100$
Relative formula mass of $S~\div ~$ relative formula mass of ${{H}_{2}}S$) $\cdot 100$
Hence, the percentage composition of $~{{H}_{2~}}$ and $S$ is $5.88$

Note :
Remember that the molar masses of various compounds are found by adding the molar masses of their individual components or elements together. To find the molar masses one should study the atomic number of various elements from the periodic table. The atomic mass or molar mass for an element is the sum of its atomic no. and the no. of neutrons present in it.