Liquid A is Concentrated Sulfuric Acid (H2SO4).

Here are the solutions to the chemistry questions:

a)

(i) Liquid A is Concentrated Sulfuric Acid ($\text{H}_2\text{SO}_4$).

(ii) The equation for the reaction between liquid A and sodium chloride is:

$$2\text{NaCl(s)} + \text{H}_2\text{SO}_4\text{(l)} \xrightarrow{\text{Heat}} \text{Na}_2\text{SO}_4\text{(s)} + 2\text{HCl(g)}$$

(iii) The type of reaction between liquid A and sodium chloride is a displacement reaction (specifically, the displacement of a volatile acid from its salt by a non-volatile acid).

(iv) The iron powder turned into a green solid, which is iron(II) chloride. Its chemical formula is $\boxed{\text{FeCl}_2}$.

(v) At the beginning, the pH of the solution in container B (Potassium hydroxide) was about 13 because potassium hydroxide (KOH) is a strong base. At the end, the pH was 3 because hydrogen chloride (HCl) gas, an acidic gas, was bubbled through the solution, neutralizing the base and eventually making the solution acidic.

b)
Apart from manganese(IV) oxide, two other substances that can be reacted with hydrochloric acid to form chlorine gas in the laboratory are:

• Potassium permanganate ($\text{KMnO}_4$)
• Potassium dichromate ($\text{K}_2\text{Cr}_2\text{O}_7$)