1g of Metal Hydroxide on heating gives 0.7g of Metal Oxide. If Molecular Mass of Metal is 90g, what will be the formula of its Chloride?

To determine the formula of the metal chloride based on the information provided, we can follow a systematic approach. We know that when 1 gram of metal hydroxide is heated, it yields 0.7 grams of metal oxide. Additionally, we have the molecular mass of the metal, which is 90 grams per mole. Let's break this down step by step.

Understanding the Reaction

When a metal hydroxide is heated, it typically decomposes into metal oxide and water. The general reaction can be represented as:

• Metal Hydroxide (MH) → Metal Oxide (MO) + Water (H₂O)

From the problem, we know that 1 g of metal hydroxide produces 0.7 g of metal oxide. This means that the remaining mass (1 g - 0.7 g = 0.3 g) is the mass of water produced during the reaction.

Calculating Molar Mass of Metal Hydroxide

Next, we need to find the molar mass of the metal hydroxide. The mass of water produced (0.3 g) can help us find the molar mass of the hydroxide. The molar mass of water (H₂O) is approximately 18 g/mol. Thus, we can calculate the moles of water produced:

• Moles of H₂O = Mass / Molar Mass = 0.3 g / 18 g/mol = 0.01667 moles

Relating Moles of Metal Hydroxide to Water

Since the decomposition of one mole of metal hydroxide produces one mole of water, the moles of metal hydroxide must also be 0.01667 moles. Now, we can find the molar mass of the metal hydroxide:

• Molar Mass of Metal Hydroxide (MH) = Mass / Moles = 1 g / 0.01667 moles ≈ 60 g/mol

Finding the Molar Mass of the Metal

The molar mass of metal hydroxide can be expressed as:

• Molar Mass of Metal Hydroxide = Molar Mass of Metal (M) + Molar Mass of Hydroxide (OH)

The molar mass of hydroxide (OH) is approximately 17 g/mol. Therefore:

• 60 g/mol = M + 17 g/mol
• M = 60 g/mol - 17 g/mol = 43 g/mol

Determining the Chloride Formula

Now that we have the molar mass of the metal (43 g/mol), we can find the formula for the metal chloride. The molar mass of chlorine (Cl) is about 35.5 g/mol. The formula for a metal chloride is typically represented as MClₓ, where x is the number of chloride ions that balance the charge of the metal.

Since the metal has a molar mass of 43 g/mol, we can assume it forms a +1 or +3 oxidation state. For simplicity, let’s consider the +1 state first:

• MCl = 43 g/mol + 35.5 g/mol = 78.5 g/mol

This is a plausible formula. However, if we consider the +3 oxidation state:

• MCl₃ = 43 g/mol + (3 × 35.5 g/mol) = 43 g/mol + 106.5 g/mol = 149.5 g/mol

Given that the molar mass of the metal is 90 g/mol, the most likely formula for the chloride, considering the common oxidation states, would be MCl₃. Therefore, the formula of the chloride of the metal is likely to be:

Final Answer

MCl₃