### Correct Option: C ### Detailed Explanation: When nitrates are heated, they undergo thermal decomposition, which means they break down into simpler substances. The behavior of different metal nitrates varies based on the metal involved. Let's analyze the decomposition of the nitrates of potassium (KNO₃), magnesium (Mg(NO₃)₂), and iron (Fe(NO₃)₃) to understand why option C is correct. 1. **Potassium Nitrate (KNO₃)**: - When heated, potassium nitrate decomposes to form potassium nitrite (KNO₂) and oxygen (O₂): \[ 2 \text{KNO}_3 (s) \rightarrow 2 \text{KNO}_2 (s) + \text{O}_2 (g) \] - This means potassium nitrate does not produce an oxide but rather a nitrite and oxygen. 2. **Magnesium Nitrate (Mg(NO₃)₂)**: - Magnesium nitrate decomposes upon heating to produce magnesium oxide (MgO), nitrogen dioxide (NO₂), and oxygen (O₂): \[ 2 \text{Mg(NO}_3)_2 (s) \rightarrow 2 \text{MgO} (s) + 4 \text{NO}_2 (g) + \text{O}_2 (g) \] - This indicates that magnesium nitrate does not produce a nitrite but rather decomposes to form an oxide and gases. 3. **Iron Nitrate (Fe(NO₃)₃)**: - Iron(III) nitrate also decomposes when heated, producing iron(III) oxide (Fe₂O₃), nitrogen dioxide (NO₂), and oxygen (O₂): \[ 2 \text{Fe(NO}_3)_3 (s) \rightarrow \text{Fe}_2\text{O}_3 (s) + 6 \text{NO}_2 (g) + 3 \text{O}_2 (g) \] - Similar to magnesium nitrate, iron nitrate decomposes to form an oxide and gases. ### Why Option C is Correct: - Option C states that the nitrates of magnesium and iron give the oxides. This is accurate because both magnesium nitrate and iron nitrate decompose to form their respective oxides (MgO and Fe₂O₃) upon heating. ### Why Other Options are Incorrect: - **Option A: All the nitrates decompose to their oxides.** - This is incorrect because potassium nitrate does not decompose to an oxide; it decomposes to a nitrite and oxygen. - **Option B: The nitrate of magnesium gives the nitrite and oxygen.** - This is incorrect because magnesium nitrate decomposes to magnesium oxide, nitrogen dioxide, and oxygen, not to a nitrite. - **Option D: The nitrate of iron gives the nitrite and oxygen.** - This is incorrect because iron nitrate decomposes to iron oxide, nitrogen dioxide, and oxygen, not to a nitrite. ### Summary of Key Points: - Potassium nitrate decomposes to form nitrite and oxygen, not an oxide. - Magnesium and iron nitrates decompose to form their respective oxides (MgO and Fe₂O₃) along with nitrogen dioxide and oxygen. - Understanding the decomposition products of metal nitrates is crucial for predicting the outcomes of thermal reactions in chemistry. - Always remember the specific decomposition pathways for different metal nitrates to avoid common pitfalls in exam questions.