Copper nitrate
Copper nitrate is the oxidizing agent as it gets reduced from +2 to 0 oxidization State and oxidize Fe from 0 to +2 state.
What you were given is the balanced chemical equation
Answer: 5.5
Explanation: Strontium titanate is both much denser (specific gravity 4.88 for natural, 5.13 for synthetic) and much softer (Mohs hardness 5.5 for synthetic, 6–6.5 for natural) than diamond.
