Given:
- Mass of silver salt of tribasic acid = 1g
- Mass of silver after heating = 0.61g

To Find:
Molecular weight of the acid

Explanation:

To find the molecular weight of the acid, we need to understand the chemical reaction that occurs during the heating process. The reaction can be represented as follows:

Ag3(A) + Heat → 3Ag + A

Where Ag3(A) represents the silver salt of the tribasic acid, Ag represents silver metal, and A represents the acid.

Step 1: Calculate the mass of silver:

The mass of silver can be calculated by subtracting the mass of silver salt before heating from the mass of silver after heating.

Mass of silver = Mass of silver salt before heating - Mass of silver after heating
= 1g - 0.61g
= 0.39g

Step 2: Calculate the moles of silver:

The moles of silver can be calculated using the molar mass of silver. The molar mass of silver is 107.87 g/mol.

Moles of silver = Mass of silver / Molar mass of silver
= 0.39g / 107.87 g/mol
= 0.00361 mol

Step 3: Calculate the moles of acid:

Since the reaction is stoichiometric, the moles of acid can be determined by using the mole ratio between silver and acid. From the balanced equation, we can see that for every 3 moles of silver, 1 mole of acid is produced.

Moles of acid = Moles of silver / 3
= 0.00361 mol / 3
= 0.00120 mol

Step 4: Calculate the molecular weight of the acid:

The molecular weight of the acid can be calculated using the moles of acid and the mass of the acid.

Molecular weight of acid = Mass of acid / Moles of acid
= 1g / 0.00120 mol
= 833.33 g/mol

Answer:
The molecular weight of the acid is 833.33 g/mol.