Statements 2 and 3 are incorrect. Galvanized pipes are used in homes. Rusting is a chemical change, not physical.

Glycerol is used to stop or slow down the decomposition of $H_2O_2$, therefore it is a negative catalyst.

The formation of a brown layer on iron (rusting) is a chemical change because iron reacts to form iron oxide, which is a new substance.

Formation of new substances is not involved in a physical change. This is a characteristic of a chemical change.

Heating of mercuric oxide leads to its decomposition into mercury and oxygen, which is a chemical change. All other options are physical changes.

Burning of coal is a type of chemical change, and since a change in which one or more new substances are formed is called a chemical change.

Anodizing is a process of forming a thick oxide layer on aluminum. This protects it from corrosion.

Molar mass of Na is 23 g/mol. 46g = 2 moles of Na. Each Na atom loses 1 electron. Electrons lost by 2 moles of Na = $2 \times 6.022 \times 10^{23} = 1.204 \times 10^{24}$.

In the above reaction, hydrogen is displaced from $NH_3$ by $O_2$ to form $NO$, so it is an example of a displacement reaction. Additionally, it is a redox (oxidation-reduction) reaction, so it also displays a reduction reaction.

According to the Law of Conservation of Mass, the total mass remains unchanged during any physical or chemical change in a closed system.

The chemical name of rust is hydrated iron(III) oxide and its general formula is $Fe_2O_3 imes H_2O$, here $Fe_2O_3$ is shown as the main component of rust.

The chemical formula of chromyl chloride is $CrO_2Cl_2$. Assuming the oxidation number of chromium is $x$: $x + 2(-2) + 2(-1) = 0 \Rightarrow x - 4 - 2 = 0 \Rightarrow x = +6$.

The bleaching property of moist $SO_2$ (in the presence of moisture) is due to its reducing capacity.

Boiling of water is only a change in its state (liquid to vapor), therefore it is a physical change.

Heating sulfide ores at high temperature in the presence of air converts them into oxides. This process is called Roasting. Example: $2ZnS + 3O_2 o 2ZnO + 2SO_2$

In this reaction, Lead (Pb) displaces Copper (Cu) from its salt solution ($CuCl_2$) because Lead is more reactive than Copper. This is a displacement reaction.

Potassium permanganate ($KMnO_4$) is a strong oxidizing agent.

In a physical change, physical properties of the substance may change, but its chemical composition (Formula) remains unchanged.

(a) Reaction of iron with steam is a displacement reaction. (b) The reaction between Sodium chloride and Silver nitrate is a double decomposition (or double displacement) reaction.

To protect iron from rust: 1. Chromium plating, 3. Applying grease, 4. Making alloys. Storing in water can increase the rate of rusting or cause rust.