# Easy Qualitative Analysis

Chemistry Level 3

A coloured compound $A$ reacts with dilute $\text{H}_{2}\text{SO}_{4}$ to produce a colourless gas $B$ and a colourless solution $C$.

The reaction between $B$ and acidified $\text{K}_{2}\text{Cr}_{2}\text{O}_{7}$ solution produces a green solution and a slightly yellowish precipitate $D$.

The substance $D$ burns in air to produce a gas $E$ which can also change the colour of $\text{K}_{2}\text{Cr}_{2}\text{O}_{7}$ solution.

When the colourless solution $C$ reacts with $\text{Pb}_{3}\text{O}_{4} / \text{H}^{+}$, the solution acquires a violet red colour due to the formation of a substance. What is this substance?

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