To calculate the percent yield of a reaction, we first need to find the theoretical yield, which is the amount of product that would be formed if the reaction proceeded perfectly according to the stoichiometry.

The balanced chemical equation given is:

2As2O3 + 3C → 3CO2 + 4As

From the equation, we can see that the molar ratio between carbon and arsenic (As) is 3:4.

Calculate the moles of carbon used:

Given mass of carbon (C) = 67g

Molar mass of carbon (C) = 12.01 g/mol

Number of moles of carbon (C) = Mass / Molar mass= 67g / 12.01 g/mol≈ 5.58 mol

Using the stoichiometry of the reaction, find the moles of As produced:

Since the ratio of carbon to As is 3:4, for every 3 moles of carbon used, 4 moles of As are produced.

Moles of As produced = (5.58 mol C) × (4 mol As / 3 mol C)≈ 7.44 molAs 

Calculate the mass of As produced:

Molar mass of As = 74.92 g/mol (from the periodic table)

Mass of As produced = Moles of As × Molar mass of As= 7.44 mol × 74.92 g/mol≈ 556.6 g

Now, the actual yield of arsenic is given as 425g.

Calculate the percent yield:

Percent yield = (Actual yield / Theoretical yield) × 100%= (425g / 556.6g) × 100%≈ 76.38%

Therefore, the percent yield of the reaction is approximately 76.38%.