Question

Which substance has a molar mass of 142 g?

Answer 1

Answer:

Molar mass of P₂O₅ = 141.948 g/mol which is approximately 142 g/mol.

Explanation:

Molar mass of AlCl₃

Molar mass  = 26.982 + 35.5 × 3 = 133.32 g/mol

Molar mass of BaCl₂

Molar mass  = 137.33 + 35.5 × 2 = 208.33 g/mol

Molar mass of MgCl₂

Molar mass  = 24.305 + 35.5×2 = 95.305 g/mol

Molar mass of P₂O₅

Molar mass  = 30.974×2 + 16× 5 = 141.948 g/mol

Answer 2

Answer:

$P_2O_5$

Explanation:

Molecular formulas is the actual number of atoms of each element in the compound. Molecular mass is the sum of the mass of each element which is present in the molecular formula is multiplied by their subscript which appear in the molecular formula.

The formula is = $AlCl_3$

Mass from the formula = 1×Mass of Aluminum + Mass of Chlorine×3 = 1×27 + 35.5×3 = 133.5 g/mol

The formula is = $BaCl_2$

Mass from the formula = 1×Mass of Barium + Mass of Chlorine×2 = 1×137 + 35.5×2 = 208 g/mol

The formula is = $MgCl_2$

Mass from the formula = 1×Mass of Magnesium + Mass of Chlorine×2 = 1×24 + 35.5×2 = 95 g/mol

The formula is = $P_2O_5$

Mass from the formula = 2×Mass of Phosphorus + Mass of oxygen×5 = 2×31 + 16×5 = 142 g/mol

Hence, correct answer is:- $P_2O_5$