1.6gof oxygen combines with20\,g20g. of a trivalent element\left( X \right)(X). The molecular mass of its sulphide is _____________ g/mol (atomic weight of S:32)

To determine the molecular mass of the sulfide of the trivalent element X, we first need to analyze the information provided and apply some basic principles of chemistry, particularly stoichiometry and the concept of valency.

Understanding the Reaction

We know that 6 g of oxygen combines with 20 g of element X. Since X is a trivalent element, it means that it can form compounds by combining with three atoms of hydrogen or two atoms of oxygen, depending on its oxidation state.

Calculating Moles of Oxygen

First, we need to calculate the number of moles of oxygen (O) used in the reaction. The molar mass of oxygen is approximately 16 g/mol. Therefore, the number of moles of oxygen can be calculated as follows:

• Moles of O = Mass of O / Molar mass of O
• Moles of O = 6 g / 16 g/mol = 0.375 moles

Determining Moles of Element X

Since oxygen typically forms oxides with elements, we can assume that the reaction involves the formation of a sulfide. Given that X is trivalent, it will combine with oxygen in a 2:3 ratio. This means that for every 2 moles of oxygen, there are 3 moles of X. We can set up a proportion to find the moles of X:

• From the stoichiometry, 2 moles of O react with 3 moles of X.
• Thus, 0.375 moles of O will react with (3/2) * 0.375 moles of X.
• Moles of X = (3/2) * 0.375 = 0.5625 moles.

Finding the Molar Mass of Element X

Now, we can calculate the molar mass of element X using its mass and the number of moles we just calculated:

• Molar mass of X = Mass of X / Moles of X
• Molar mass of X = 20 g / 0.5625 moles ≈ 35.56 g/mol.

Calculating the Molecular Mass of the Sulfide

The sulfide of element X would be represented as X₂S, where S is sulfur. Since we know the atomic weight of sulfur is 32 g/mol, we can now calculate the molecular mass of the sulfide:

• Molecular mass of X₂S = (2 * Molar mass of X) + (1 * Atomic weight of S)
• Molecular mass of X₂S = (2 * 35.56 g/mol) + (1 * 32 g/mol)
• Molecular mass of X₂S = 71.12 g/mol + 32 g/mol = 103.12 g/mol.

Final Result

Thus, the molecular mass of the sulfide of the trivalent element X is approximately 103.12 g/mol.