Answer:
Step-by-step explanation:
Cr₂O₃ ( chromium oxide )
Mass of Cr₂O₃⁻ = 2 x 52 + 3 x 16 = 104 + 48 = 152
152 gram chromium oxide contains 104 grams chromium
152 tonnes chromium oxide contains 104 tonnes chromium
5 tonnes chromium oxide contains 104 x 5 / 152 tonnes chromium
mass of chromium required = 104 x 5 / 152 tonnes
= 3.42 tonnes .