Question 14 Marks
Read the passage given below and answer the following questions from 1 to 5. Since the isotopes have the same electronic Configuration, they have almost the same Chemical properties.The only difference is in Their rates of reactions, mainly due to their Different enthalpy of bond dissociation . However, in physical properties these Isotopes differ considerably due to their large Mass differences. There are a number of methods for preparing Dihydrogen from metals and metal hydrides. 1.) Laboratory Preparation of Dihydrogen – It is usually prepared by the reaction of Granulated zinc with dilute hydrochloric. $Zn + 2H + \rightarrow Zn_2+ + H_2$ It can also be prepared by the reaction of Zinc with aqueous alkali. $Zn + 2NaOH \rightarrow Na_2ZnO_2 + H_2$ Commercial Production of Dihydrogen – The commonly used processes are outlined Below: i) Electrolysis of acidified water using Platinum electrodes gives hydrogen. ii) High purity (> 99.95%) dihydrogen is Obtained by electrolysing warm aqueous Barium hydroxide solution between nickel iii) It is obtained as a by product in the Manufacture of sodium hydroxide and Chlorine by the electrolysis of brine Solution. During electrolysis, the reactions That take place are: at anode: $2\text{CI}(\text{aq})\rightarrow\text{CI}_2(\text{g})+2\bar{\text{e}}$ at cathode: $2\text{H}_2\text{O}(\text{l})+2\text{e}\rightarrow\text{H}_2(\text{g})+2\text{O}\bar{\text{H}}(\text{aq})$ The overall reaction is $2\text{Na }(\text {aq})+2\text{C}\bar{\text{I}}(\text{aq})+2\text{H}_2\text{O}(\text{l})$ $\text{CI}_2(\text{g})+\text{H}_2(\text{g})+2\text{Na}^+(\text{aq})+2\text{O}\bar{\text{H}}(\text{aq})$ That take place are: iv) Reaction of steam on hydrocarbons or coke At high temperatures in the presence of Catalyst yields hydrogen.
The mixture of $CO$ and $H_2$ is called water Gas. As this mixture of $CO$ and $H_2$ is used for The synthesis of methanol and a number of Hydrocarbons, it is also called synthesis gas Or ‘syngas’. Nowadays ‘syngas’ is produced From sewage, saw-dust, scrap wood, Newspapers etc. The process of producing ‘syngas’ from coal is called ‘coal gasification’. The production of dihydrogen can be Increased by reacting carbon monoxide of Syngas mixtures with steam in the presence of Iron chromate as catalyst. This is called water-gas shift reaction. Carbon dioxide is removed by scrubbing with Sodium arsenite solution. Presently ~77% of the industrial Dihydrogen is produced from petro-chemicals, 18% from coal, 4% from electrolysis of aqueous Solutions and 1% from other sources. Physical Properties Dihydrogen is a colourless, odourless, Tasteless, combustible gas. It is lighter than Air and insoluble in water. Its other physical Properties are alongwith those of deuterium. The chemical behaviour of dihydrogen (and for That matter any molecule) is determined, to a Large extent, by bond dissociation enthalpy. The H–H bond dissociation enthalpy is the Highest for a single bond between two atoms Of any element. What inferences would you Draw from this fact ? It is because of this factor That the dissociation of dihydrogen into its Atoms is only~0.081% around 2000K which Increases to 95.5% at 5000K. Also, it is Relatively inert at room temperature due to the high H–H bond enthalpy. Thus, the atomic Hydrogen is produced at a high temperature In an electric arc or under ultraviolet Radiations. Since its orbital is incomplete with 1s1 Electronic configuration, it does combine With almost all the elements. It accomplishes Reactions by
i) loss of the only electron to Give H+, ii) gain of an electron to form H–, and iii) Sharing electrons to form a single covalent bond. The chemistry of dihydrogen can be Illustrated by the following reactions: Reaction with halogens: It reacts with Halogens, $X_2$ to give hydrogen halides, $\text{H}_2(\text{g})+\text{x}_2(\text{g})\rightarrow2\text{HX}(\text{g})(\text{x}=\text{F.CI.Br.I})$ While the reaction with fluorine occurs even in The dark, with iodine it requires a catalyst. Reaction with dioxygen: It reacts with Dioxygen to form water. The reaction is highly Exothermic. $2\text{H}_2(\text{g})+\text{O}_2(\text{g})\xrightarrow{\text{catalyst or beading}}2\text{H}_2\text{O}(\text{l}):$ $\triangle\text{H}^-=-285.9\text{kj}\text{mol}^-1$ This is the method for the manufacture of Ammonia by the Haber process. Reactions with metals: With many metals it Combines at a high temperature to yield the Corresponding hydrides $H_2$ (g) + 2M (g) → 2 MH (s); Where M is an alkali metal Reactions with metal ions and metal Oxides: It reduces some metal ions in aqueous Solution and oxides of metals (less active than Iron) into corresponding metals. $\text{H}_2(\text{g})+\text{Pd}^{2+}\text{(aq)}\rightarrow\text{Pd}(\text{s})+2\text{H}^+(\text{aq})$ $\text{y}\text{H}_2(\text{g})+\text{M}_\text{x}\text{O}_\text{y}(\text{S})\rightarrow\text{xM}(\text{s})+\text{y}\text{H}_2\text{O}\text{(l)}$ Reactions with organic compounds: It Reacts with many organic compounds in the Presence of catalysts to give useful Hydrogenated products of commercial Importance. For example: Hydrogenation of vegetable oils using Nickel as catalyst gives edible fats (margarine and vanaspati ghee) Hydroformylation of olefins yields Aldehydes which further undergo Reduction to give alcohols. $\text{H}_2+\text{CO}+\text{RCH}=\text{CH}_2\rightarrow\text{RCH}_2\text{CH}_2\text{CHO}$ $\text{H}_2+\text{RCH}_2\text{CH}_2\text{CHO}\rightarrow\text{RCH}_2\text{CH}_2\text{CH}_2\text{OH}$
The mixture of $CO$ and $H_2$ is called water Gas. As this mixture of $CO$ and $H_2$ is used for The synthesis of methanol and a number of Hydrocarbons, it is also called synthesis gas Or ‘syngas’. Nowadays ‘syngas’ is produced From sewage, saw-dust, scrap wood, Newspapers etc. The process of producing ‘syngas’ from coal is called ‘coal gasification’. The production of dihydrogen can be Increased by reacting carbon monoxide of Syngas mixtures with steam in the presence of Iron chromate as catalyst. This is called water-gas shift reaction. Carbon dioxide is removed by scrubbing with Sodium arsenite solution. Presently ~77% of the industrial Dihydrogen is produced from petro-chemicals, 18% from coal, 4% from electrolysis of aqueous Solutions and 1% from other sources. Physical Properties Dihydrogen is a colourless, odourless, Tasteless, combustible gas. It is lighter than Air and insoluble in water. Its other physical Properties are alongwith those of deuterium. The chemical behaviour of dihydrogen (and for That matter any molecule) is determined, to a Large extent, by bond dissociation enthalpy. The H–H bond dissociation enthalpy is the Highest for a single bond between two atoms Of any element. What inferences would you Draw from this fact ? It is because of this factor That the dissociation of dihydrogen into its Atoms is only~0.081% around 2000K which Increases to 95.5% at 5000K. Also, it is Relatively inert at room temperature due to the high H–H bond enthalpy. Thus, the atomic Hydrogen is produced at a high temperature In an electric arc or under ultraviolet Radiations. Since its orbital is incomplete with 1s1 Electronic configuration, it does combine With almost all the elements. It accomplishes Reactions by
i) loss of the only electron to Give H+, ii) gain of an electron to form H–, and iii) Sharing electrons to form a single covalent bond. The chemistry of dihydrogen can be Illustrated by the following reactions: Reaction with halogens: It reacts with Halogens, $X_2$ to give hydrogen halides, $\text{H}_2(\text{g})+\text{x}_2(\text{g})\rightarrow2\text{HX}(\text{g})(\text{x}=\text{F.CI.Br.I})$ While the reaction with fluorine occurs even in The dark, with iodine it requires a catalyst. Reaction with dioxygen: It reacts with Dioxygen to form water. The reaction is highly Exothermic. $2\text{H}_2(\text{g})+\text{O}_2(\text{g})\xrightarrow{\text{catalyst or beading}}2\text{H}_2\text{O}(\text{l}):$ $\triangle\text{H}^-=-285.9\text{kj}\text{mol}^-1$ This is the method for the manufacture of Ammonia by the Haber process. Reactions with metals: With many metals it Combines at a high temperature to yield the Corresponding hydrides $H_2$ (g) + 2M (g) → 2 MH (s); Where M is an alkali metal Reactions with metal ions and metal Oxides: It reduces some metal ions in aqueous Solution and oxides of metals (less active than Iron) into corresponding metals. $\text{H}_2(\text{g})+\text{Pd}^{2+}\text{(aq)}\rightarrow\text{Pd}(\text{s})+2\text{H}^+(\text{aq})$ $\text{y}\text{H}_2(\text{g})+\text{M}_\text{x}\text{O}_\text{y}(\text{S})\rightarrow\text{xM}(\text{s})+\text{y}\text{H}_2\text{O}\text{(l)}$ Reactions with organic compounds: It Reacts with many organic compounds in the Presence of catalysts to give useful Hydrogenated products of commercial Importance. For example: Hydrogenation of vegetable oils using Nickel as catalyst gives edible fats (margarine and vanaspati ghee) Hydroformylation of olefins yields Aldehydes which further undergo Reduction to give alcohols. $\text{H}_2+\text{CO}+\text{RCH}=\text{CH}_2\rightarrow\text{RCH}_2\text{CH}_2\text{CHO}$ $\text{H}_2+\text{RCH}_2\text{CH}_2\text{CHO}\rightarrow\text{RCH}_2\text{CH}_2\text{CH}_2\text{OH}$
- The mixture of CO and H2 is called …
- water Gas
- Dry ice
- Dry carbon
- Dry hydrogen
- Which of the following is not physical property of Dihydrogen.
- colourless
- Highest dissociation enthalpy
- odourless
- Tasteless
- Dihydrogen is reacts with dioxygen to get ….
- $H_2O_2$
- $2H_2O_2$
- $2H_2O$
- $H_2O$
- High purity dihydrogen is obtained by electrolysing warm aqueous barium hydroxide solution between… electrodes.
- Chromium
- Copper
- Platinum
- Nickel
Answer
View full question & answer→- (a) water gas
- (b) Highest dissociation enthalpy
- (c) $2H_2O$
- (d) Nickel
