Which of the following statements is incorrect?

Options

A. In Half - Heroult process, the electrolyte used is a molten mixture of alumina, sodium hydroxide and cryolite.
B. Lead is extracted form its chief ore by both carbon reduction and self reduction..
C. Tin is extracted from its chief ore by carbon monoxide reduction.
D. Siderite and cassiterite are carbonate ores.

Answer

To determine which statement is incorrect from the options provided, let's analyze each statement step by step.

### Step 1: Analyze the Hall-Herault Process
The Hall-Herault process is used for the extraction of aluminum. In this process, alumina (Al₂O₃) is dissolved in molten cryolite (Na₃AlF₆) along with some sodium hydroxide (NaOH).

**Conclusion**: The statement regarding the Hall-Herault process is correct.

### Step 2: Lead Extraction
Lead can be extracted from its sulfide ore (PbS) through both carbon reduction and self-reduction. When PbS is heated in the presence of oxygen, it forms lead oxide (PbO) and sulfur dioxide (SO₂). The lead oxide can then be reduced back to lead using PbS again.

**Conclusion**: The statement about lead extraction is correct.

### Step 3: Tin Extraction
Tin (Sn) is extracted from its ore, cassiterite (SnO₂), typically through carbon monoxide reduction. This process involves reducing SnO₂ with carbon monoxide (CO) to obtain tin.

**Conclusion**: The statement about tin extraction is correct.

### Step 4: Identify the Ore Types
Ciderite is indeed FeCO₃ (a carbonate ore), while cassiterite is SnO₂ (an oxide ore). Therefore, one of the statements claims that both are not carbonate, which is true since cassiterite is an oxide.

**Conclusion**: The statement regarding the types of ores is correct.

### Final Conclusion
Since all analyzed statements A, B, C, and D are found to be correct, we need to identify which one is incorrect based on the context provided in the question. The statement regarding the classification of ores is misleading because it suggests that both ores are not carbonate, which is incorrect since ciderite is indeed a carbonate ore.

### Answer
The incorrect statement is: "Ciderite ore is FeCO₃ and cassiterite ore is SnO₂ so this is cassiterite and this is ciderite one of them is carbonate incorrect statement."

---