Answer:
39.7%
Explanation:
To obtain the percentage composition of chromium (Cr) in Na₂Cr₂O₇, do the following:
Molar mass of Na₂Cr₂O₇ = (23×2) + (52×2) + (16×7)
= 46 + 104 + 112
= 262 g/mol
Mass of Cr in Na₂Cr₂O₇ = 2 × 52 = 104 g
Percentage composition of Cr = mass of Cr / Molar mass of Na₂Cr₂O₇ × 100
= 104 / 262 × 100
= 39.7%
Thus, the percentage composition of chromium (Cr) in Na₂Cr₂O₇ is 39.7%
