Which of the following is the best starting material for the preparation of oxygen? Heating of trioxonitrate (v) with

Analysis of the Question

The question asks for the best starting material (a metal) to heat with a trioxonitrate(V) salt to produce oxygen gas. In chemistry, the thermal decomposition of metal nitrates follows a specific pattern based on the reactivity series of the metals.

Concept Explanation

When metal trioxonitrates(V) (nitrates) are heated, they decompose. The products depend on the position of the metal in the reactivity series:

1. Group 1 Metals (e.g., Na, K): These decompose to form the metal trioxonitrite(III) (nitrite) and oxygen gas. • Equation: $2NaNO_3(s) \rightarrow 2NaNO_2(s) + O_2(g)$
2. Metals between Lead and Copper: These decompose to form the metal oxide, nitrogen(IV) oxide, and oxygen gas.
3. Noble Metals (e.g., Ag, Au): These decompose to form the metal, nitrogen(IV) oxide, and oxygen gas.

The question asks for the "best starting material" for the preparation of oxygen. While heating sodium trioxonitrate(V) ($NaNO_3$) alone produces oxygen, the question specifically asks for the reaction of a trioxonitrate(V) with a metal.

When we heat a metal trioxonitrate(V) with a reactive metal like Sodium (Na), the sodium acts as a reducing agent, effectively pulling oxygen away from the nitrate to form the nitrite or oxide, thereby releasing oxygen gas efficiently.

Step-by-Step Solution

1. Identify the reaction type: This is a redox reaction where the metal reduces the nitrate salt.
2. Evaluate the options: • Pb, Zn, Ca: These metals are less reactive than Sodium. While they can participate in various chemical reactions, Sodium is the most reactive metal among the choices provided. • Na (Sodium): Sodium is highly reactive. When sodium trioxonitrate(V) is heated with sodium, the reaction is highly favorable for the liberation of oxygen because sodium has a very high affinity for oxygen, driving the decomposition process forward.
3. Conclusion: In the context of laboratory preparation and chemical reactivity, Sodium ($Na$) is the most effective choice to facilitate the release of oxygen from the nitrate salt.

This aligns with the principle that more reactive metals are more effective at driving the decomposition of nitrates to release oxygen.

Exam Tip

Always remember the "Reactivity Series" (Potassium, Sodium, Calcium, Magnesium, Aluminum, Zinc, Iron, Lead, Copper, Mercury, Silver, Gold). Metals higher up the series are stronger reducing agents. If you see a question about "best starting material" or "best reducing agent," look for the metal highest on the reactivity series!