Chlorine is liberated, when we heat

Options

A. `KMnO_4+NaCl`
B. `K_2Cr_2O_7+MnO_2`
C. `Pb(NO_(3))_(2)+MnO_(2)`
D. `K_2Cr_2O_7+HCl`

Answer

To solve the question "Chlorine is liberated when we heat," we need to identify the correct chemical reaction that produces chlorine gas upon heating.

### Step-by-Step Solution:

1. **Identify the Reactants**: We are looking for a reaction involving a compound that can release chlorine gas (Cl2) when heated. Common candidates include potassium dichromate (K2Cr2O7) and hydrochloric acid (HCl).

2. **Write the Reaction**: The relevant reaction is:
\[ K_2Cr_2O_7 + 14 HCl \rightarrow 2 KCl + 2 CrCl_3 + 7 H_2O + 3 Cl_2 \]
This equation shows that potassium dichromate reacts with hydrochloric acid to produce potassium chloride (KCl), chromium(III) chloride (CrCl3), water (H2O), and chlorine gas (Cl2).

3. **Balancing the Reaction**:
- Count the number of each type of atom on both sides of the equation to ensure they are equal.
- The balanced equation shows that for every 1 mole of K2Cr2O7, 14 moles of HCl are required, producing 2 moles of KCl, 2 moles of CrCl3, 7 moles of water, and 3 moles of Cl2.

4. **Conclusion**: Based on the reaction, we can conclude that chlorine gas is liberated when potassium dichromate is heated in the presence of hydrochloric acid. Therefore, the correct option is D.

### Final Answer:
The correct answer is option D.