Chemistry

34. Option (i) and (iv)

Pig iron is the iron obtained from the blast that has many impurities (Mn, P, Si, etc.) and approximately 4% carbon content. When it is re-melted or cast with the help of scrap iron, then it has less carbon content i.e. 3% as compared to pig iron.

The Zr andTi are purified by the help of Arkel Method that contain the following reaction: 

Zr (s) + 2I₂   ZrI₄ ( g)  Zr Pure  (s) + 2I₂

Ti + 2I₂  TiI₄  Ti + 2I₂

Here we obtain Zr and Ti as a pure form of solid when purified using the Arkel method.

13. 2Cu²⁺  +    4I^-  → Cu₂I₂ + I₂

When Cu²⁺  reacts with potassium iodide white precipitate of Cu₂I₂ is formed.

12. Transition elements have the ability to involve their d-electrons along with their s-electrons in the process of bond formation. This results in formation of strong metal-metal bonds which makes their melting point high. 

11. Cr (24)= [Ar]3d⁵4s²

Zn  (30) =  [Ar] 3d¹⁰4s² 

The stability of orbitals according to the electrons filled is in order: 

Fully filled > half-filled > partially filled 

As 3d¹⁰ is completely filled orbital of Zn  is more stable than the 3d⁵ half-filled orbital of Cr . It is comparatively easy to remove electron from 3d⁵ than from 3d¹⁰. 

Therefore, the first ionization enthalpy of Cr is lower than that of Zn. 

32. Option (i)

According to the above graph, at point D the equivalent value of ΔG for the reduction of FeO is approximately 330 units for the particular temperature. Also, for CO the equivalent value of Δ?  at the particular temperature for point D  is around −330 units. Thus, if we calculate the overall value of ΔG for the reduction of FeO with carbon monoxide then it is almost zero at point D.

31. Option (i)

Below point A, only the value of ΔG (CO, CO₂) is less than the value of ΔG (Fe, FeO) at the corresponding temperatures. Thus, only carbon monoxide will be able to reduce FeO to Fe and will get itself oxidized into CO₂.

30. Option (iv)

Above point A, ΔG (C, CO)

29. Option (i) 

The cyanide process involves 3 steps:

First step - The finely grounded ore of gold and silver are made to come in contact with the solution containing the cyanide,

Second step - it involves separation of gold and silver from the cyanide solution  

Third step - it involves the recovery of gold and silver in their pure forms precipitating the remaining solution with zinc dust.

Thus, the metal is recovered by displacing Zn with the metal (Au or Ag) from metal ions.

28. Option (i)

The electrolytic method can be used to purify zinc and copper. The impure metal is used as an anode in this method. As the cathode, a pure strip of the same metal is used. They are immersed in an appropriate electrolytic bath containing a soluble salt of the same metal.

The more basic metals remain in the solution, while the less basic metals are transferred to the anode mud.