When 16.8 g of a white solid X was heated 4.4 g of an acid gas A which turned lime water milky, was driven off together with 1.8 g of a gas B which condensed to a colourless liquid. The solid that remained Y dissolved in water to give an alkaline solution which with excess barium chloride solution gave a white precipitate Z. The precipitate effervesced with acid giving carbon dioxide. Identify A,B and Y and write the equation for the thermal decomposition of X.

Explanation

To solve the problem, we need to identify the substances A, B, and Y, and write the equation for the thermal decomposition of solid X. Let's break it down step by step:

### Step 1: Identify the gases A and B
- **Gas A**: The problem states that gas A is an acid gas that turns lime water milky. This indicates that gas A is likely carbon dioxide (CO₂), as it reacts with calcium hydroxide (lime water) to form calcium carbonate, which is a white precipitate that makes the solution milky.

- **Gas B**: The problem mentions that gas B condenses to a colorless liquid. Given that gas A is CO₂, gas B is likely water (H₂O), which is also a colorless liquid.

### Step 2: Identify the solid Y
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