Attempt all the questions
Group A
11x1=11
Rewrite the correct options for each question in your answer sheet.
1. 2R-OH+2Na --> 2RONa+H2, is an example of
A) acidic nature of alcohol
B) basic nature of alcohol
C) electrophilic substitution reaction
D) nucleophilic substitution reaction
= basic nature of alcohol
2.C6H5CH2-CHO and C6H5CHO can be distinguished by:
A) Iodoform test
B) Tollen's test
C) 2, 4 - DNP test
D) Fehling test
= 2, 4 - DNP test
A) CH3CHO
B) CH3CH2-OH
C) CH3-CO-CH3
D) CH3-O-CH3
= CH3-CO-CH3
B) 2
C) 3
D) 4
= 3
B) P2O5
C) CH3COONa
D) CH3COOH
= Conc.H2SO4
B) 2
C) 3
D) 4
= 2
B) 7
C) 8
D) more than 8
= less than 7
B) it lowers the activation energy
C) it increases the activation energy
D) it forms complex with the reaction
= it lowers the activation energy
B) 0.5M
C) 1M
D) 2M
= 0.25M
B) Hg2O
C) HgO2
D) Hg2O2
= Hg2O
B) Sn and Cu
C) Zn and Pb
D) Zn, Cu, and Sn
= B) Sn and Cu
Group B 8x5=40
12. An electrochemical cell is constructed by using aluminum and silver electrodes whose electrodes' potential values are; (1+1+2+1)
E° Al3+/Al = -1.67V
E° Ag+/Ag = 0.80V
i) What is meant by electrochemical cell?
Ans:- An electrochemical cell is a device that uses chemical reactions to generate an electric current or uses an electric current to cause chemical reactions.
ii) Represent an electrochemical cell using the above electrodes
Ans:- Al(s) | Al3+(aq) || Ag+(aq) | Ag(s)
iii) Write down complete cell reactions
Ans:- The complete cell reaction can be written as:
Al(s) + 3Ag+(aq) → Al3+(aq) + 3Ag(s)
iv) Calculate the emf of the cell.
Ans:- The EMF of the cell can be calculated using the Nernst equation:
EMF = E°cell - (RT/nF)ln(Q)
where E°cell is the standard cell potential, R is the gas constant, T is the temperature in kelvin, n is the number of moles of electrons transferred in the cell reaction, F is the Faraday constant, and Q is the reaction quotient.
The reaction quotient for the cell reaction is:
Q = [Al3+]/([Ag+]^3)
At standard conditions, the EMF of the cell is:
EMF = E°cell - (0.0257/3)ln([Al3+]/[Ag+]^3)
EMF = (0.80 V) - (0.00857)ln([Al3+]/[Ag+]^3)
Substituting the given values, we get:
EMF = 1.47 V (rounded to two decimal places)
Therefore, the EMF of the electrochemical cell is 1.47 V.
Or
Hess's law is applied to calculate the different types of enthalpy of reactions (1+1+3)
i) Define Hess's Law of constant heat summation.
Ans:- Hess's Law of constant heat summation states that the total enthalpy change of a chemical reaction is independent of the pathway between the initial and final states. In other words, if a chemical reaction can be expressed as a series of intermediate steps, then the overall enthalpy change of the reaction is equal to the sum of the enthalpy changes of the individual steps.
ii) What is meant by the enthalpy of reaction?
Ans:- Enthalpy of reaction is the amount of heat energy released or absorbed during a chemical reaction under constant pressure. It is usually denoted by ΔH and is expressed in units of joules or kilojoules per mole of reactants or products.
iii) Standard enthalpy of formation of H2O2(l) and H2O (l) is 188kj/mol and 286 KJ/mol respectively. What will be the enthalpy change of the following reaction:
2H2O2(l) --> 2H2O(l)+O2(g).
Ans:- To calculate the enthalpy change of the given reaction using Hess's Law, we need to write it as a combination of reactions for which the enthalpy change is known.
First, we reverse the second reaction and multiply its enthalpy change by -1 to get:
H2O(l) + 1/2O2(g) --> H2O2(l) ΔH = -286 kJ/mol
Next, we multiply the first reaction by 2 to get:
2H2O2(l) --> 2H2O(l) + O2(g) ΔH = 2 x 188 kJ/mol = 376 kJ/mol
Finally, we add the two reactions to get the desired reaction:
2H2O(l) + O2(g) --> 2H2O2(l) ΔH = -286 kJ/mol + 376 kJ/mol = 90 kJ/mol
Therefore, the enthalpy change of the given reaction is 90 kJ/mol, which indicates that the reaction is exothermic (i.e., heat is released during the reaction).
13. Ionic product of water at 25° C is 1x10ˆ-14 and water is a very weak electrolyte. (1+1+2+1)
i) Define the ionic product of water.
Ans:- The ionic product of water, also known as the ionization constant of water, is the product of the concentrations of the hydrogen ions (H+) and hydroxide ions (OH-) in pure water at a given temperature. It is denoted by Kw and can be expressed as Kw = [H+][OH-].
ii) Deduce the reaction Kw = [H+] [OH]
Ans:- The reaction that gives rise to the ionic product of water is the self-ionization of water, which can be represented as:
H2O(l) ⇌ H+(aq) + OH-(aq)
The equilibrium constant for this reaction is the ionization constant of water (Kw), and it can be expressed as:
Kw = [H+][OH-]
iii) Calculate the [OH-] concentration of 0.01M HCL at 25°C
Ans:- To calculate the [OH-] concentration of 0.01 M HCl at 25°C, we can use the fact that HCl is a strong acid and dissociates completely in water to produce H+ ions and Cl- ions. Therefore, the [H+] concentration in the solution is 0.01 M.
Using the Kw expression, we have:
Kw = [H+][OH-]
1 x 10^-14 = (0.01 M) [OH-]
[OH-] = 1 x 10^-12 M
Therefore, the [OH-] concentration of the solution is 1 x 10^-12 M.
iv) What is the effect of temperature on the ionic product of water?
Ans:- The ionic product of water (Kw) increases with temperature. This is because the self-ionization of water is an endothermic process, meaning that it absorbs heat. As temperature increases, more heat energy is available for the self-ionization of water to occur, resulting in an increase in the concentrations of H+ and OH- ions and an increase in the value of Kw. Conversely, as temperature decreases, the self-ionization of water becomes less favorable, resulting in a decrease in the value of Kw.
14. Ethyl alcohol is common alcohol and is used to manufacture alcoholic beverages. It can be prepared from sugar-containing materials like molasses by a fermentation process. (1+1+1+1+1)
i) Define fermentation
Ans:- Fermentation is a metabolic process that converts sugars into other organic compounds, such as alcohol and lactic acid, in the absence of oxygen. It is an anaerobic process that is commonly used in the production of alcoholic beverages and other fermented foods.
ii) What is meant by molasses?
Ans:- Molasses is a viscous, dark syrup that is produced as a byproduct during the processing of sugar cane, sugar beets, or sorghum. It contains a high concentration of sucrose, as well as other sugars, minerals, and vitamins.
iii) MEntion the function of yeast in the fermentation of ethyl alcohol.
Ans:- Yeast is a type of microorganism that plays a crucial role in the fermentation of ethyl alcohol. Yeast consumes the sugars present in the molasses and produces alcohol and carbon dioxide as byproducts. The carbon dioxide gas produced during fermentation is responsible for the characteristic fizziness of carbonated alcoholic beverages.
iv) Write a chemical reaction for the conversion of cane sugar into ethyl alcohol.
Ans:- The chemical reaction for the conversion of cane sugar into ethyl alcohol can be represented as:
C6H12O6 → 2 C2H5OH + 2 CO2
In this reaction, cane sugar (C6H12O6) is broken down into two molecules of ethyl alcohol (C2H5OH) and two molecules of carbon dioxide (CO2) in the presence of yeast.
v) Give a difference between absolute alcohol and denatured alcohol.
Ans:- Absolute alcohol is pure alcohol (ethanol) that has been distilled to remove all impurities and water. It is used primarily in scientific and medical applications.
Denatured alcohol, on the other hand, is a type of alcohol that has been treated with additives, such as methanol, to make it unfit for consumption. It is used in a variety of industrial applications, such as as a solvent, fuel, or cleaning agent, and is generally cheaper than absolute alcohol.
15. A carbonyl compound (M) contains three carbon atoms and it undergoes the iodoform test.
i) identify the compound (M)
Ans:- The carbonyl compound (M) that contains three carbon atoms and undergoes the iodoform test is propanal (CH3CH2CHO).
ii) write down a chemical reaction for the preparation of (M)
Ans:- Propanal can be prepared by the oxidation of 1-propanol using an oxidizing agent such as potassium permanganate (KMnO4):
CH3CH2CH2OH + [O] → CH3CH2CHO + H2O
iii) How is (M) converted into propane?
Ans:- Propanal (M) can be converted into propane by a reduction reaction using a reducing agent such as lithium aluminum hydride (LiAlH4):
CH3CH2CHO + 2[H] → CH3CH2CH3
iv) Predict the final product obtained when (M) is treated with CH 3Mgl in presence of dry ether and followed by hydrolysis?
Ans:- When propanal (M) is treated with CH3MgI in the presence of dry ether, followed by hydrolysis, the final product obtained is 2-methyl-2-propanol (tert-butyl alcohol):
CH3CH2CHO + CH3MgI → CH3CH2CH(OMgI)CH3 CH3CH2CH(OMgI)CH3 + H2O → CH3CH2CHO + (CH3)3COH
v) Give a laboratory test reaction of the carbonyl compound.
Ans:- One laboratory test reaction of a carbonyl compound is the Tollens' test. In this test, a small amount of silver nitrate (AgNO3) is added to the carbonyl compound in the presence of sodium hydroxide (NaOH) and heated. The presence of an aldehyde or ketone is indicated by the formation of a silver mirror on the inside of the reaction vessel.
Or
Convert ethoxy ethane from a halo alkane C2H 5Br by using Williamson's reaction.(1+2+2)
i) What product is obtained when ethoxyethane is heated with excess Hl?
Ans:- When ethoxyethane is heated with excess Hl (hydrogen iodide), the product obtained is ethanol and ethyl iodide. The reaction can be represented as follows:
C2H5OC2H5 + 2HI → C2H5I + C2H5OH + H2O
ii) Why are old samples of ether not distilled to dryness in the air?
Ans:- Old samples of ether are not distilled to dryness in the air because ether is highly volatile and can easily form explosive peroxides when exposed to air, light, and heat. These peroxides are highly unstable and can explode upon distillation or even upon exposure to shock.
iii) Convert phenol into anisole.
Ans:- To convert phenol into anisole, we can use the Williamson's ether synthesis by reacting phenol with methyl iodide in the presence of a strong base such as sodium hydride. The reaction can be represented as follows:
C6H5OH + CH3I → C6H5OCH3 + HI
Overall, the reaction involves the substitution of the hydroxyl group (-OH) in phenol with a methoxy group (-OCH3) from methyl iodide. The product obtained is anisole, which is also known as methoxybenzene.
16. For the following reaction sequence.
i) Write down reagents and conditions for reaction (1), reaction (2), reaction (3), and reaction (4).
ii) Identify the compound (z) giving IUPAC name. (4+1)
17. How would you apply Hoffmann's method for the separation of 1°, 2°, and 3° amine from their mixture? (5)
= Hofmann's method is a chemical method used for the separation of primary (1°), secondary (2°), and tertiary (3°) amines from their mixture. The separation is based on the fact that when an amine is treated with chloroform (CHCl3) and excess bromine (Br2) in the presence of aqueous sodium hydroxide (NaOH), the reaction proceeds through the formation of an isocyanide intermediate, which upon hydrolysis gives an amine that is one carbon shorter than the original amine.
The procedure for Hofmann's method for the separation of 1°, 2°, and 3° amines from their mixture is as follows:
To the amine mixture, add chloroform (CHCl3) and excess bromine (Br2) dropwise while stirring continuously. The reaction mixture turns yellow due to the formation of N-bromoalkylamine.
After the addition of CHCl3 and Br2, add a cold aqueous solution of NaOH to the reaction mixture slowly while stirring continuously. The reaction mixture now turns colorless and a white precipitate of the isocyanide intermediate is formed.
Allow the reaction mixture to stand for some time at room temperature, and then filter the precipitated isocyanide intermediate.
Wash the isocyanide intermediate with water and then hydrolyze it by treating it with dilute hydrochloric acid (HCl) or dilute sulfuric acid (H2SO4) to obtain the amine that is one carbon shorter than the original amine.
Repeat the above steps 1 to 4 with fresh quantities of CHCl3, Br2, and NaOH to separate the remaining amines.
The separated amines can be identified by their physical and chemical properties, such as boiling point, melting point, and spectroscopic data.
Note: Hofmann's method is not applicable for the separation of quaternary ammonium salts or heterocyclic amines, which do not undergo the Hofmann degradation reaction.
18. An important compound nontypical transition metal zinc which is used as an eye lotion and is also called white vitriol. (5x1)
i) Write down a method of preparation of white vitriol.
Ans:-White vitriol is the common name for zinc sulfate heptahydrate, which can be prepared by the reaction of zinc oxide (ZnO) or zinc metal (Zn) with sulfuric acid (H2SO4). The reaction can be represented as follows:
ZnO + H2SO4 + 7H2O → ZnSO4·7H2O
ii) What happens when white vitriol is heated to 800°C?
Ans:-When white vitriol is heated to 800°C, it undergoes dehydration, and water molecules are lost, leading to the formation of anhydrous zinc sulfate (ZnSO4). The reaction can be represented as follows:
ZnSO4·7H2O → ZnSO4 + 7H2O
iii) Define double salt giving an example of it
Ans:- A double salt is a type of compound that contains two different cations and/or anions, held together by ionic bonds. These salts are formed by the combination of two simple salts, and they retain their individual identities in the solid state. An example of a double salt is carnallite, which is a naturally occurring mineral that contains magnesium chloride and potassium chloride.
iv) How is Lithopone obtained from white vitriol.
Ans:-Lithopone is a white pigment that is used in paints, coatings, and plastics. It is prepared by the reaction of zinc sulfate and barium sulfate (BaSO4) in the presence of reducing agents such as carbon black or hydrogen sulfide. The reaction can be represented as follows:
ZnSO4 + BaSO4 + 2H2S → ZnS·BaSO4 + 2H2O
The resulting product is a mixture of zinc sulfide (ZnS) and barium sulfate (BaSO4) in a 1:1 molar ratio, which is then washed, dried, and milled to obtain a fine powder.
v) Why is zinc considered a non-typical transition metal.
Ans:- Zinc is considered a non-typical transition metal because it does not exhibit some of the characteristic properties of transition metals, such as variable oxidation states, the formation of colored compounds, and the ability to form complex ions. Zinc has a full d subshell in its ground state electron configuration, which makes it less likely to participate in typical transition metal reactions. Additionally, zinc has a relatively low melting and boiling point compared to other transition metals, and it is more reactive with acids and bases.
19. Steel manufactured by open Hearth process. (1+2+1+1)
i) What is the open Heart process?
ii) Write down the chemical reactions occurring in Open-Hearth Furnace.
iii) Why is Speigeleisen added in the Open-Hearth Furnace?
iv) Write down the composition of stainless steel.
Group C 3x8=24
20. a) Write an example of each of the following reactions.
i) Hydroboration oxidation
ii) Decarbonylation
iii) Sandmeyer's reaction
iv) iodoform reaction
v) Elimination reaction
vi) Cannizzaro's reaction
vii) Reimer-Tiemann reaction
viii) Fridel Craft alkylation
Or
An unsaturated hydrocarbon (C3H6) undergoes Markovikov's rule to give (A). Compound (A) is hydrolyzed with aqueous alkali to yield (B). When (B) is treated with PBr3, compound (C) is produced. (C) reacts with AgCN (alc.) to give another compound (D). The compound (D) if reduced with LiAlH4, produces (E).
i) Define Markovikov's rule.
ii) Identify (A), (B), (C), (D) and (E) with chemical reaction.
iii) How does E react with nitrous acid?
iv) How would you convert (B) into C3H8? (1+5+1+1)
21. a) For a hypothetical chemical reaction mP + n Q--> z; the rate Law is, rate = K [P]ˆm [Q]ˆn. Where K is the rate constant of the reaction (m+n) is the overall order. (4+1)
i) Define rate Law.
ii) Why is rate law an experimental parameter?
iii) What is meant by the rate constant?
iv) Mention a difference between the order and molecularity of a reaction.
b) For the above reaction, the order reaction with respect to P and Q are first order and Zero order respectively. Experimental data obtained from the reaction are; as below.
table
i) Identify the value of A, B, and C
ii0 Calculate rate constant [K]. (3+1)
Or
a) Crystal of oxalic acid is generally used to prepare a primary standard solution. (1+1+1+1)
i) Define the Primary Standard solution.
ii) Which chemical indicator is used in the titration of KMnO4 solution versus oxalic acid solution?
iv) Mention a major application of titration in a quality control laboratory.
b) An aqueous solution of a dibasic acid containing 17.7 gm of an acid per liter of the solution, has a density of 1.0077 gm/liter (molar mass of the acid = 118gm/mol) Calculate; i) molarity ii) morality (2+2)
22. a) i) What is Portland cement?
ii) Name the major components present in Portland cement.
iii) Why is gypsum used in clinker during the cement production process?
iv) Give any two instruments used for quality control of cement. (1+1+1+1)
b) i) Differentiate between homo-polymer and co-polymer given an example of each.
ii) Name the monomers of the following polymer and also write their molecular formula.
a) Polystyrene
b) Bakelite. (2+2)
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