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Zorluk: OrtaNitrogen Gas, Nitrogen Cycle, and Oxides of Nitrogen

During the laboratory preparation and isolation of nitrogen gas from atmospheric air, a student must pass atmospheric air through several reagents in a specific sequence to remove impurities. What is the correct order of steps to isolate nitrogen gas from atmospheric air, starting from the initial removal of carbon(IV) oxide to the final collection of the gas?

  1. 1Pass atmospheric air through concentrated potassium hydroxide (KOHKOH) or sodium hydroxide (NaOHNaOH) solution to absorb carbon(IV) oxide (CO2CO_2).
  2. 2Bubble the gas mixture through concentrated tetraoxosulfate(VI) acid (H2SO4H_2SO_4) or over fused calcium chloride (CaCl2CaCl_2) to absorb water vapor.
  3. 3Pass the dried gas mixture over red-hot copper turnings in a heated combustion tube to absorb oxygen (O2O_2).
  4. 4Collect the unreactive residual nitrogen gas (containing approximately 1% noble gases) over water in a gas jar.

Cevap

The correct sequence to isolate nitrogen gas from atmospheric air is: 1. Pass air through concentrated caustic alkali solution (KOHKOH/NaOHNaOH) to remove CO2CO_2. 2. Pass the gas through concentrated H2SO4H_2SO_4 to remove water vapor. 3. Pass dry gas over red-hot copper turnings to remove O2O_2. 4. Collect the remaining nitrogen gas over water.
Atmospheric air consists primarily of N2N_2 (78%), O2O_2 (21%), CO2CO_2 (0.03%), water vapor, and noble gases. To isolate nitrogen, impurities are removed according to chemical reactivity: CO2CO_2 is removed first by neutralisation with an alkali (KOHKOH), moisture is absorbed by a dehydrating agent (concentrated H2SO4H_2SO_4), oxygen is removed by reduction of red-hot copper turnings to CuOCuO, and the remaining nitrogen gas (mixed with trace noble gases like argon) is collected over water.

Adım Adım Çözüm

1
Identify the acidic gas impurity in air and select its removal agent.
Carbon(IV) oxide (CO2CO_2) is acidic and must be scrubbed first using concentrated KOHKOH or NaOHNaOH solution: 2KOH(aq)+CO2(g)→K2CO3(aq)+H2O(l)2KOH_{(aq)} + CO_{2(g)} \rightarrow K_2CO_{3(aq)} + H_2O_{(l)}.
Removing CO2CO_2 first prevents it from contaminating subsequent drying and heating apparatus.
2
Dry the remaining gas mixture.
Passing the remaining gases (O2O_2, N2N_2, water vapor, noble gases) through concentrated H2SO4H_2SO_4 absorbs moisture.
Gas must be thoroughly dried before passing over hot copper turnings to prevent thermal shock and unwanted reactions.
3
Remove oxygen gas chemically.
Passing dry air over red-hot copper turnings removes O2O_2: 2Cu(s)+O2(g)→2CuO(s)2Cu_{(s)} + O_{2(g)} \rightarrow 2CuO_{(s)}.
Hot copper chemically binds oxygen, leaving only unreactive nitrogen and traces of noble gases.
4
Collect the purified nitrogen gas.
Nitrogen gas is collected over water.
Nitrogen has very low solubility in water, making water displacement ideal for gas collection.

Anahtar Kavram

Laboratory Isolation of Nitrogen from Atmospheric Air
Tahmini Süre:1m 30s
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Konular

Nitrogen Gas, Nitrogen Cycle, and Oxides of Nitrogen

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