1.72 g elemental arsenic combined with excess chlorine gas to form 4.17 g of the arsenic chloride compound. If the molar mass is between 180-200 g/mol, write the balanced equation for this synthesis process.

As + 3/2 Cl₂ → AsCl₃

Explanation:

The reaction of the problem is:

As + Cl₂ → AsₐClₓ

The problem consist in determine a and x from the formula to write the balanced equation.

1.72g of As are (Molar mass: 74.92g/mol):

1.72g * (1mol / 74.92g) = 0.02296 moles of As are added to the reaction.

As molar mass of the arsenic chloride is between 180-200g/mol, the moles produced are between:

4.17g * (1 mol / 180g) = 0.0232

4.17g * (1 mol / 200g) = 0.0209

As moles of As are 0.02296 the most logic is than 1 mole of As produce 1 mole of the compound, that means the arsenic compound contains 1 mole in each formula:

As₁Clₓ: AsClₓ

And also, 0.02296 moles of AsClₓ are produced, the molar mass is:

4.17g / 0.02296mol = 181.62g/mol.

The atom of As weighs 74.92g/mol. The mass of the chlorides is:

181.62 - 74.92 = 106.70g/mol.

1 atom of Cl weighs 35.45g/mol:

106.70g/mol / 35.45g/mol = 3.0 atoms of Cl are in the chemical formula, that is:

AsCl₃

And the balanced equation for this synthesis is:

As + Cl₂ → AsCl₃

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