Answer:
As + 3/2 Cl₂ → AsCl₃
Step-by-step 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
As + 3/2 Cl₂ → AsCl₃