Answer:
The chemical symbol for this element is La
Explanation:
Step 1: Data given
Mass of XCl3 = 0.760 grams
Mass of XI3 = 1.610 grams
Molar mass Cl = 35.45 g/mol
Step 2: The balanced equation
2XCl3 + 3I2 → 2XI3 + 3Cl2
The mol ratio for XCl3: XI3 = 2:2 or 1:1
Step 3: Calculate moles
Moles = mass / molar mass
Moles XCl3 = mass XCl3 / molar mass XCl3
Moles XCl3 = 0.760 grams / (X + 3*35.45 g/mol)
Moles XI3 = 1.610 grams / (X + 3*126.9 g/mol)
0.760 grams / (X + 3*35.45 g/mol) = 1.610 grams / (X + 3*126.9 g/mol)
0.760 / (X + 106.35) = 1.610 / (X + 380.7)
0.760 (X +380.7) = 1.610 ( X + 106.35)
0.760X + 289.3 = 1.610X + 171.2
118.1 = 0.85X
X = 138.9 g/mol
If we look for an element with atomic mass of 138.9 g/mol we find Lanthanum (La)
2LaCl3 + 3I2 → 2LaI3 + 3Cl2