Question

Give a practical laboratory method that you might use to produce small quantities of the following gases and comment on any difficulties that might arise: (a) \(\mathrm{O}_{2} ;\) (b) \(\mathrm{NO} ;\) (c) \(\mathrm{H}_{2} ;\) (d) \(\mathrm{NH}_{3} ;\) (e) \(\mathrm{CO}_{2}\).

Short answer

The gases are produced in the following ways: \(O_2\) through decomposition of \(H_2O_2\), \(NO\) by the reduction of concentrared \(HNO_3\) by copper, \(H_2\) by the reaction of zinc with \(H_2SO_4\), \(NH_3\) by the reaction of \(NH_4Cl\) with \(NaOH\) and \(CO_2\) by the reaction of \(CaCO_3\) with \(HCl\). Safety measures should be adhered to due to the potentially harmful and corrosive substances used.

Step-by-step solution

Production of Oxygen (\(O_2\))

Oxygen can be generated in a lab by the decomposition of hydrogen peroxide (\(H_2O_2\)). This is usually done by adding a catalyst like manganese dioxide (\(MnO_2\)) to speed up the reaction. The reaction is: \(2H_2O_2 \rightarrow 2H_2O + O_2\). The difficulty in this method is handling the manganese dioxide catalyst as it is harmful when inhaled or swallowed.

Production of Nitric Oxide (\(NO\))

Nitric oxide can be produced by the reduction of concentrated nitric acid (\(HNO_3\)) by copper. The reaction is: \(3Cu + 8HNO_3 \rightarrow 3Cu(NO_3)_2 + 2NO + 4H_2O\). The difficulty in this method could be handling of the nitric acid as it is quite corrosive.

Production of Hydrogen (\(H_2\))

Hydrogen can be produced in the lab by the reaction between zinc and sulfuric acid (\(H_2SO_4\)). The reaction is: \(Zn + H_2SO_4 \rightarrow ZnSO_4 + H_2\). The difficulty could be the handling of sulfuric acid which is corrosive and can cause burns.

Production of Ammonia (\(NH_3\))

In a lab, ammonia can be prepared by the reaction of a salt like ammonium chloride (\(NH_4Cl\)) with a strong alkali like sodium hydroxide (\(NaOH\)). The reaction is: \(NH_4Cl + NaOH \rightarrow NaCl + NH_3 + H_2O\). A challenge in this method is that the resulting ammonia gas has a strong smell and is harmful if inhaled.

Production of Carbon Dioxide (\(CO_2\))

Carbon dioxide can be made in the lab by reacting calcium carbonate (\(CaCO_3\)) with hydrochloric acid (\(HCl\)). The reaction is: \(CaCO_3 + 2HCl \rightarrow CaCl_2 + CO_2 + H_2O\). The difficulty could be handling hydrochloric acid which is a strong acid and can cause burns.

Key concepts

Oxygen Production

Oxygen is an essential element for many laboratory experiments and is often produced through the decomposition of hydrogen peroxide (\(H_2O_2\)). In this method, a catalyst like manganese dioxide (\(MnO_2\)) is used to speed up the reaction, which produces water and releases oxygen gas. The reaction is: \[2H_2O_2 \rightarrow 2H_2O + O_2\]While this is a relatively straightforward method, it requires caution. Manganese dioxide can be harmful if inhaled or ingested, so proper handling and protective gear are essential. Additionally, careful control of the reaction is needed to prevent rapid decomposition, which can be hazardous.

Nitric Oxide Generation

Nitric oxide (\(NO\)) can be produced in the laboratory by reducing concentrated nitric acid (\(HNO_3\)) using copper. The chemical equation for this reaction is: \[3Cu + 8HNO_3 \rightarrow 3Cu(NO_3)_2 + 2NO + 4H_2O\]One of the main challenges in this procedure is handling nitric acid due to its corrosive nature. Appropriate safety measures, such as wearing gloves and goggles, are crucial to minimize risks. The pungent nature and potential health hazards associated with nitric oxide also call for a well-ventilated workspace.

Hydrogen Preparation

Hydrogen (\(H_2\)) is a commonly used gas in labs and can be produced by reacting zinc with sulfuric acid (\(H_2SO_4\)). The reaction proceeds as follows:\[Zn + H_2SO_4 \rightarrow ZnSO_4 + H_2\]Sulfuric acid is corrosive and can cause serious burns if mishandled. Thus, it’s essential to conduct this method with caution. Use protective clothing and eye protection, and work in a controlled environment to safely harvest the hydrogen gas produced. Given hydrogen's flammable nature, always ensure that the area is free from open flames during preparation.

Ammonia Synthesis

Ammonia (\(NH_3\)) is another crucial gas in chemical laboratories and can be synthesized by reacting ammonium chloride (\(NH_4Cl\)) with sodium hydroxide (\(NaOH\)). The reaction is depicted as follows:\[NH_4Cl + NaOH \rightarrow NaCl + NH_3 + H_2O\]One significant challenge when synthesizing ammonia is managing its distinctive and overwhelming odor, which can be harmful if inhaled. It is important to perform this process in a fume hood or a well-ventilated area while using appropriate protective equipment such as masks and gloves.

Carbon Dioxide Production

Carbon dioxide (\(CO_2\)) is easily generated in the laboratory environment by reacting calcium carbonate (\(CaCO_3\)) with hydrochloric acid (\(HCl\)). The reaction unfolds as:\[CaCO_3 + 2HCl \rightarrow CaCl_2 + CO_2 + H_2O\]While this method is simple, handling hydrochloric acid requires care due to its potentially corrosive properties. Proper protective clothing and goggles are advised. Additionally, this process should be carried out in an area with good ventilation to safely manage the release of carbon dioxide gas.