Question

0.5 g sample of copper ore is converted into solution. The resulting solution is acidified with and excess KI added. The liberated requires 0.248g for complete reaction. Find the percentage of Cu in the ore

Answer 1

0.5g sample of copper ore is converted into solution. The resulting solution is acidified with and excess KI added. The liberated 0.248g Na2S2O3.5H2O for complete reaction.

To find : The percentage of Cu in the ore.

solution : here equivalents of copper = equivalents of KI = equivalents of Na2S2O3.5H2O

molar mass of Na2S2O3.5H2O = 248g/mol

given mass of Na2S2O3.5H2O = 0.248g

so no of moles of Na2S2O3.5H2O = 0.248/248 = 10¯³

so, equivalents of Cu = 10¯³

⇒mass of Cu/equivalent wt of Cu = 10¯³

⇒mass of Cu/(63.5/1) = 10¯³ [ as n - factor of Cu in copper ore, Cu₂O is 1]

⇒mass of Cu = 0.0635

percentage of Cu in the ore = mass of Cu/mass of sample × 100

= 0.0635/0.5 × 100

= 6.35/0.5

= 12.7 %

Therefore the percentage of Cu in copper ore is 12.7 %.