Preparation and Properties of Hydrogen, Oxygen, Nitrogen and Carbon dioxide, Oxidation and Reduction
Preparation and Properties of Hydrogen, Oxygen, Nitrogen and Carbon dioxide, Oxidation and Reduction MCQ Questions
7.
In the laboratory, hydrogen gas is commonly prepared by the reaction of granulated zinc with:
A.
Concentrated nitric acid
B.
Distilled water at room temperature
C.
Sodium hydroxide solution only
D.
Dilute hydrochloric acid or dilute sulphuric acid
ANSWER :
D. Dilute hydrochloric acid or dilute sulphuric acid
Approach
The question asks about the common laboratory preparation method for hydrogen gas using granulated zinc. We need to evaluate the reactivity of zinc with various substances provided in the options to determine which reaction safely and efficiently produces hydrogen gas.
Step-by-step
- Recall the reactivity series: Zinc is a metal that is more reactive than hydrogen. This means it can displace hydrogen from acids.
- Consider the reaction with acids: Metals above hydrogen in the reactivity series react with dilute acids to produce hydrogen gas and a salt.
- Evaluate option D (Dilute hydrochloric acid or dilute sulphuric acid): Granulated zinc reacts readily with dilute hydrochloric acid (\(\text{HCl}\)) or dilute sulphuric acid (\(\text{H}_2\text{SO}_4\)) to produce hydrogen gas. The reactions are:
\[\text{Zn(s)} + 2\text{HCl(aq)} \rightarrow \text{ZnCl}_2\text{(aq)} + \text{H}_2\text{(g)}\]
\[\text{Zn(s)} + \text{H}_2\text{SO}_4\text{(aq)} \rightarrow \text{ZnSO}_4\text{(aq)} + \text{H}_2\text{(g)}\]
These reactions are safe, controllable, and commonly used in laboratories for hydrogen preparation.
- Evaluate other options:
- Concentrated nitric acid: Nitric acid is a strong oxidizing agent. When it reacts with metals like zinc, it typically produces oxides of nitrogen (\(\text{NO}_2\), \(\text{NO}\), \(\text{N}_2\text{O}\)) instead of hydrogen gas.
- Distilled water at room temperature: Zinc is not reactive enough to displace hydrogen from water at room temperature. More reactive metals like sodium or potassium react with cold water, but zinc requires steam to react slowly.
- Sodium hydroxide solution only: Zinc is an amphoteric metal, meaning it can react with strong bases like sodium hydroxide solution to produce hydrogen gas, forming zincates. For example:
\[\text{Zn(s)} + 2\text{NaOH(aq)} \rightarrow \text{Na}_2\text{ZnO}_2\text{(aq)} + \text{H}_2\text{(g)}\]
However, this reaction is generally slower and less preferred for common laboratory preparation compared to the reaction with dilute acids. The question asks for the commonly prepared method, and dilute acids are the standard choice.
- Conclusion: The reaction of granulated zinc with dilute hydrochloric acid or dilute sulphuric acid is the most common and suitable laboratory method for preparing hydrogen gas.
Correct Option: D) Dilute hydrochloric acid or dilute sulphuric acid
Incorrect Options
- A) Concentrated nitric acid — Concentrated nitric acid is a strong oxidizing agent and reacts with zinc to produce oxides of nitrogen, not hydrogen gas.
- B) Distilled water at room temperature — Zinc is not reactive enough to react with cold water to produce hydrogen gas.
- C) Sodium hydroxide solution only — While zinc can react with strong bases
8.
Dilute nitric acid is generally avoided for the laboratory preparation of hydrogen gas by reaction with a metal because:
A.
It does not react with metals at all
B.
It reacts too slowly to be useful
C.
It produces only oxygen gas instead
D.
Nitric acid is a strong oxidising agent and reduces the liberated hydrogen further to oxides of nitrogen or water
ANSWER :
D. Nitric acid is a strong oxidising agent and reduces the liberated hydrogen further to oxides of nitrogen or water
Approach
The question asks why dilute nitric acid is generally not used for the laboratory preparation of hydrogen gas by reacting with a metal. This involves understanding the chemical properties of nitric acid, particularly its oxidizing nature.
Step-by-step
- Understanding the Goal: The objective is to produce hydrogen gas (\(\text{H}_2\)) by reacting a metal with an acid. A typical reaction for this is: \(\text{Metal} + \text{Acid} \rightarrow \text{Salt} + \text{Hydrogen gas}\).
- Properties of Nitric Acid: Nitric acid (\(\text{HNO}_3\)) is known to be a strong oxidizing agent. This means it readily accepts electrons and gets reduced itself.
- Reaction with Metals: When a metal reacts with an acid, the metal typically gets oxidized (loses electrons) and the hydrogen ions (\(\text{H}^+\)) from the acid get reduced to hydrogen gas (\(\text{H}_2\)).
- The Problem with Nitric Acid: Because nitric acid is a strong oxidizing agent, it oxidizes the hydrogen gas (\(\text{H}_2\)) that is produced. Instead of escaping as a gas, the hydrogen is further oxidized to water (\(\text{H}_2\text{O}\)) or the nitrogen in nitric acid gets reduced to various oxides of nitrogen (e.g., \(\text{NO}\), \(\text{NO}_2\), \(\text{N}_2\text{O}\)).
- Result: This secondary reaction prevents the collection of pure hydrogen gas, or significantly reduces its yield, making dilute nitric acid unsuitable for this purpose. For example, with zinc:\[ \text{Zn} + 4\text{HNO}_3 \text{ (dilute)} \rightarrow \text{Zn(NO}_3\text{)}_2 + 2\text{NO}_2 + 2\text{H}_2\text{O} \]
Here, instead of \(\text{H}_2\), oxides of nitrogen are formed.
Correct Option:
D) Nitric acid is a strong oxidising agent and reduces the liberated hydrogen further to oxides of nitrogen or water. This statement accurately describes why dilute nitric acid is not used for preparing hydrogen gas. The strong oxidizing nature of nitric acid causes it to react with the nascent hydrogen, preventing its evolution as a gas.
Incorrect Options:
- A) It does not react with metals at all — This is incorrect. Nitric acid does react with many metals, but the products are not primarily hydrogen gas due to its oxidizing nature.
- B) It reacts too slowly to be useful — While reaction rates can vary, the primary reason for avoiding nitric acid is not its slow reaction rate, but the nature of the products formed.
- C) It produces only oxygen gas instead — This is incorrect. Nitric acid does not typically produce oxygen gas when reacting with metals. It produces oxides of nitrogen or water, not oxygen.
9.
On an industrial scale, hydrogen is manufactured in large quantities by passing steam over hot coke. This process is commonly known as:
C.
The Bosch process (steam-coke reaction producing water gas)
ANSWER :
C. The Bosch process (steam-coke reaction producing water gas)
Approach
The question asks to identify the industrial process for manufacturing hydrogen by passing steam over hot coke. This is a well-known chemical process in industrial chemistry.
Step-by-step
- The reaction described is steam reacting with hot coke (carbon). This reaction produces carbon monoxide and hydrogen gas, commonly known as water gas. The chemical equation is:
\[ \text{C(s)} + \text{H}_2\text{O(g)} \xrightarrow{\text{High Temperature}} \text{CO(g)} + \text{H}_2\text{(g)} \]- This specific method of producing hydrogen (and carbon monoxide) from steam and hot coke is historically and industrially known as the Bosch process.
- The Bosch process is an industrial method for producing hydrogen gas. It involves two main steps: first, the production of water gas (a mixture of carbon monoxide and hydrogen) by passing steam over red-hot coke, and then the water-gas shift reaction to convert carbon monoxide into more hydrogen. However, the initial reaction of steam over hot coke to produce water gas is the core of what is referred to as the Bosch process in this context.
Correct Option:
C) The Bosch process (steam-coke reaction producing water gas) is the correct answer. This process specifically refers to the industrial method of producing hydrogen by reacting steam with hot coke.
Incorrect Options
- A) The Solvay process — This process is used for the industrial production of sodium carbonate (washing soda) from sodium chloride, ammonia, and carbon dioxide. It does not involve hydrogen manufacturing from steam and coke.
- B) The Contact process — This process is used for the industrial manufacture of sulfuric acid (\(\text{H}_2\text{SO}_4\)) from sulfur dioxide and oxygen. It does not involve hydrogen manufacturing.
- D) The Haber process — This process is used for the industrial synthesis of ammonia (\(\text{NH}_3\)) from nitrogen and hydrogen. While it uses hydrogen, it is not a method for manufacturing hydrogen from steam and coke; rather, it consumes hydrogen produced by other means (like the Bosch process or steam reforming of natural gas).
10.
Electrolysis of acidified/alkaline water produces hydrogen gas at the:
B.
Both electrodes equally
Approach
To determine where hydrogen gas is produced during the electrolysis of water, we need to understand the basic principles of electrolysis, specifically the reactions occurring at the anode and cathode.
Step-by-step
- Understanding Electrolysis: Electrolysis is the process of using electrical energy to drive a non-spontaneous chemical reaction. In the electrolysis of water, water molecules are split into hydrogen and oxygen gases.
- Electrodes: An electrolytic cell has two electrodes: the anode (positive electrode) and the cathode (negative electrode). Oxidation occurs at the anode, and reduction occurs at the cathode.
- Reactions in Acidified/Alkaline Water:
- At the Cathode (Reduction): Water molecules gain electrons to form hydrogen gas and hydroxide ions. The general reaction is:
\[ 2\text{H}_2\text{O}(l) + 2\text{e}^- \rightarrow \text{H}_2(g) + 2\text{OH}^-(aq) \]
In acidic solutions, \(\text{H}^+\) ions are present, and the reaction is:
\[ 2\text{H}^+(aq) + 2\text{e}^- \rightarrow \text{H}_2(g) \]
In both cases, hydrogen gas is produced at the cathode.
- At the Anode (Oxidation): Water molecules lose electrons to form oxygen gas and hydrogen ions. The general reaction is:
\[ 2\text{H}_2\text{O}(l) \rightarrow \text{O}_2(g) + 4\text{H}^+(aq) + 4\text{e}^- \]
In alkaline solutions, hydroxide ions are present, and the reaction is:
\[ 4\text{OH}^-(aq) \rightarrow \text{O}_2(g) + 2\text{H}_2\text{O}(l) + 4\text{e}^- \]
In both cases, oxygen gas is produced at the anode.
- Conclusion: Since hydrogen gas is formed by the gain of electrons (reduction), it is produced at the cathode.
Correct Option: A) Cathode
Incorrect Options
- B) Both electrodes equally — Hydrogen gas is produced only at the cathode, and oxygen gas is produced at the anode. They are not produced equally at both electrodes.
- C) Neither electrode — This is incorrect as hydrogen gas is definitely produced during the electrolysis of water.
- D) Anode — Oxygen gas is produced at the anode, not hydrogen gas.
11.
During the electrolysis of water, hydrogen and oxygen gases are liberated in the volume ratio of:
Approach
To determine the volume ratio of hydrogen and oxygen gases liberated during the electrolysis of water, we need to understand the chemical reaction involved and the stoichiometry of the products.
Step-by-step
- Understand Electrolysis of Water: Electrolysis of water is the process of decomposing water (\(\text{H}_2\text{O}\)) into its constituent elements, hydrogen gas (\(\text{H}_2\)) and oxygen gas (\(\text{O}_2\)), by passing an electric current through it.
- Write the Balanced Chemical Equation: The unbalanced equation for the decomposition of water is:\( \text{H}_2\text{O} \rightarrow \text{H}_2 + \text{O}_2 \)To balance this equation, we need two molecules of water to produce two molecules of hydrogen and one molecule of oxygen:\[ 2\text{H}_2\text{O} \rightarrow 2\text{H}_2 + \text{O}_2 \]
- Determine the Molar Ratio: From the balanced chemical equation, we can see that 2 moles of water decompose to produce 2 moles of hydrogen gas and 1 mole of oxygen gas. Therefore, the molar ratio of hydrogen to oxygen is 2:1.
- Relate Molar Ratio to Volume Ratio (Avogadro's Law): According to Avogadro's Law, under the same conditions of temperature and pressure, equal volumes of all gases contain an equal number of moles. This implies that the volume ratio of gases is directly proportional to their molar ratio.Since the molar ratio of hydrogen gas to oxygen gas is 2:1, their volume ratio will also be 2:1.
Correct Option: B) During the electrolysis of water, hydrogen gas and oxygen gas are liberated in a volume ratio of 2:1, as derived from the balanced chemical equation.
Incorrect Options
- A) 1:1 — This ratio would imply that one molecule of water produces one molecule of hydrogen and one molecule of oxygen, which is not stoichiometrically possible for water decomposition.
- C) 3:1 — This ratio is incorrect and does not align with the balanced chemical equation for water electrolysis.
- D) 1:2 — This ratio suggests that for every one volume of hydrogen, two volumes of oxygen are produced, which is the inverse of the correct ratio and contradicts the stoichiometry.
12.
The commercial process in which hydrocarbons/natural gas (methane) react with steam in the presence of a nickel catalyst at high temperature to produce hydrogen is called:
B.
Fractional distillation
ANSWER :
A. Steam reforming
Approach
The question asks to identify the commercial process where hydrocarbons (specifically methane) react with steam in the presence of a nickel catalyst at high temperatures to produce hydrogen. This is a direct recall question related to industrial chemical processes.
Step-by-step
- The process described involves methane (\(\text{CH}_4\)), steam (\(\text{H}_2\text{O}\)), a nickel catalyst, high temperature, and the production of hydrogen (\(\text{H}_2\)).
- This specific reaction is known as steam reforming, particularly steam-methane reforming (SMR), which is the most common industrial method for producing hydrogen.
- The chemical reaction can be represented as:
\[ \text{CH}_4 \text{(g)} + \text{H}_2\text{O} \text{(g)} \xrightarrow{\text{Ni catalyst, high temp}} \text{CO} \text{(g)} + 3\text{H}_2 \text{(g)} \]- This reaction is highly endothermic and typically occurs at temperatures between 700-1100 °C.
Correct Option: A) Steam reforming is the commercial process that fits the description, where methane reacts with steam over a nickel catalyst at high temperatures to produce hydrogen.
Incorrect Options
- B) Fractional distillation is a process used to separate components of a liquid mixture based on differences in their boiling points, commonly used in petroleum refining. It does not involve chemical reactions to produce hydrogen.
- C) The Ostwald process is a chemical process used for the production of nitric acid (\(\text{HNO}_3\)). It involves the catalytic oxidation of ammonia. It is unrelated to hydrogen production from methane and steam.
- D) Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. It is commonly used in the production of alcohol, lactic acid, etc., but not for industrial hydrogen production from methane and steam.
