Untitled Quiz

Protection of Fe by Coating with Zn

• This process is called galvanization.

Conductivity

• The expression for conductivity (k) is: k = 1/R x cell const.

Molar Conductivity of a Weak Electrolyte

• Molar conductivity of a weak electrolyte increases with decreasing concentration.

Relation Between G & Ecell

• The relation between G and Ecell is: G =  nFEcell

Primary Cell

• A primary cell is a type of electrochemical cell in which the redox reaction occurs only once.

Electrolyte Used in Fuel Cell

• Concentrated aqueous KOH is the electrolyte used in fuel cells.

Conductors of Electricity

• C2H5OH is not a good conductor of electricity.

Balancing Redox Reactions

• The number of electrons required to balance the following equation NO3- + 4 H+ + e- -> 2 H2O + NO is 3.

Electric Charge for Reduction

• The amount of electric charge required for the reduction of 1 mole of Cr2O72- into Cr3+ is 6F. This is because the reduction involves the transfer of 6 electrons.

Faraday's Law of Electrolysis

• One Faraday of electricity passed through a solution of CuSO4 will deposit 63.5 g of Cu.

Equivalent Conductance of a Strong Electrolyte

• An increase in the equivalent conductance of a strong electrolyte with dilution is mainly due to an increase in the ionic mobility of ions.

0m (NH4OH)

• 0m (NH4OH) is equal to 0m (NH4Cl) + 0m (NaOH) - 0m (NaCl)

The Salt Bridge in Galvanic Cells

• The salt bridge in a galvanic cell prevents the diffusion of ions from one electrode to another.

Silver as a Transition Element

• Although silver has a completely filled outermost orbit in its ground state, it is considered a transition element because its d orbital is incomplete in its +1 oxidation state.

Oxidizing Power in the Series VO2+ < Cr2O72- < MnO4-

• The increasing oxidizing power in the series is attributed to the increasing stability of the lower oxidation state of the metal ion. The higher the stability of the lower oxidation state, the stronger the oxidizing power of the metal ion.

Irregular Variation of Ionization Enthalpy in First-Row Transition Series

• The irregular variation of ionization enthalpy in the first-row transition series is due to the interplay of factors such as electronic configuration, screening effect, and interelectronic repulsions.

Stronger Reducing Agent, Cr2+ or Fe1+

• Cr2+ is a stronger reducing agent than Fe1+, because Cr2+ has a greater tendency to lose electrons and get oxidized to Cr3+.

Highest Oxidation State of a Metal in Oxides or Fluorides

• The highest oxidation state of a metal is exhibited in its oxides or fluorides because oxygen and fluorine are highly electronegative elements and can stabilize the higher oxidation states of the metal by withdrawing electron density.

Magnetic Moment of Mn2+

• The magnetic moment of Mn2+ is 5.92 BM (Bohr magnetons). This can be calculated using the formula √n(n+2) BM, where n is the number of unpaired electrons.

Magnetic Properties of Fe2+ and Fe3+

• Fe2+ is more magnetic than Fe3+ because it has more unpaired electrons.

Disproportionation of an Oxidation State

• Disproportionation of an oxidation state refers to a reaction where a single element in a specific oxidation state is simultaneously oxidized and reduced.

Variable Oxidation States of Lanthanides

• Lanthanides exhibit variable oxidation states due to the presence of closely spaced 4f and 5d orbitals, which can participate in bonding.

Lanthanide Contraction

• Lanthanide contraction is the decrease in atomic and ionic radii of lanthanide elements as we move from left to right across the series. This is due to the poor shielding effect of 4f electrons.

Oxidation States of Lanthanoids

• The most common oxidation state of lanthanoids is +3, but they can also exhibit +2 and +4 oxidation states.

High Enthalpies of Atomization of Transition Metals

• The high enthalpies of atomization of transition metals are due to the strong metallic bonding resulting from the involvement of d electrons in bonding.

Catalytic Activity of Transition Metals

• Transition metals and their compounds are excellent catalysts because they can exist in multiple oxidation states and readily form complexes or intermediates, which facilitates chemical reactions.

Unstable ‘d’ Configuration

• The ‘d’ configuration is unstable because it represents a state where electrons are not optimally arranged in terms of energy and stability. Transition metals try to achieve a more stable configuration by losing or gaining electrons, leading to the formation of various oxidation states and complex ions.

Transition Element

• A transition element is defined as an element whose atom has an incomplete d subshell in its elemental state or in one of its common oxidation states.
• Three characteristics of transition elements are as follows:
• Variable oxidation States: Transition metals exhibit variable oxidation states due to the involvement of both (n-1)d and ns electrons in bonding.
• Formation of Coloured Compounds: Transition metal compounds are generally colored due to the d-d electronic transitions, where electrons in the d orbitals absorb specific wavelengths of light and emit complementary colours.
• Formation of Complexes: Transition metals can form complexes because their small ionic size, high charge density, and availability of vacant d orbitals enable them to coordinate with ligands, forming complex ions.

Lanthanoid Contraction

• The Lanthanoid contraction is the steady decrease in atomic and ionic radii of the lanthanide elements progressing from left to right across the series.
• Consequences of Lanthanide Contraction:
• Similar Properties of succeeding elements: Because of the contraction, the size of the atoms of the elements after lanthanides becomes similar to the size of the elements preceding lanthanides.
• Effect on the properties of the 4d and 5d transition series: It influences the properties of the 4d and 5d transition series, impacting their chemical behavior and physical characteristics.

Electronic Configurations of Lanthanoids

• The electronic configuration of lanthanoids is [Xe] 4f1-14 5d0 − 1 6s2.
• Stable +3 oxidation state: The most stable oxidation state for lanthanoids is +3 due to the half-filled or completely filled 4f orbitals, which contributes to greater stability.

Reasons for Properties of Transition Metals

• (i) Basic nature of the lowest oxide of transition metal and acidic nature of the highest oxide: The lowest oxide, with a lower oxidation state of the metal, forms ionic bonds, resulting in basic nature. As the oxidation state increases, the covalent character prevails, leading to an acidic nature of the oxide.
• (ii) Highest oxidation state exhibited in oxo-anions: The highest oxidation state of a transition metal is generally exhibited in its oxo-anions, which are formed by the metal atom combining with oxygen atoms.
• (iii) Color of the compounds: Transition metal compounds are generally colored due to the presence of unpaired d electrons, which can undergo d-d electronic transitions, absorbing specific wavelengths of light and emitting complementary colors.

Formation of Complex Compounds

• (a) Transition metals form complex compounds due to the availability of vacant d orbitals for bonding, their moderate size, and high charge density. These factors allow them to coordinate with ligands, forming coordination complexes.
• (b) Effective atomic number rule: The Effective atomic number rule suggests that the metal atom in a coordination complex tends to achieve an electronic configuration resembling that of the nearest inert gas.

Interstitial Compounds

• Interstitial compounds are formed when small nonmetal atoms like hydrogen, boron, carbon, or nitrogen are trapped in the interstitial spaces of metallic lattices. These compounds are hard, high-melting point materials with unique properties.

D.D.T.

• D.D.T. (Dichloro Diphenyl Trichloroethane) is a colorless, crystalline insecticide that gained widespread popularity in the 1940s for its effectiveness in controlling mosquitoes and malaria-transmitting insects. However, its extensive use has been severely restricted due to its long-term accumulation in the environment, its persistence, and its adverse effects on wildlife and human health.

Preparation of Diethyl Ether from Ethyl Chloride

• Ethyl chloride can be converted to diethyl ether by reacting it with alcoholic potassium hydroxide (KOH). The reaction proceeds through a Williamson ether synthesis mechanism:

  2CH3CH2Cl + 2KOH (alc) --> CH3CH2OCH2CH3 + 2KCl + H2O

Reaction of Silver Acetate with Bromine

• When silver acetate is treated with bromine, it undergoes a reaction to form ethyl bromide, carbon dioxide, and silver bromide:

  CH3COOAg + Br2 --> CH3CH2Br + CO2 + AgBr

Conversion of Ethyl Alcohol to Ethene

• The reaction sequence is as follows:

  C2H5OH conc   A .H 2 SO4 Br2 B alc KOH  C

• A: CH3CH2Br (ethyl bromide)

• B: CH3CH2Br (ethyl bromide)

• C: CH2=CH2 (ethene)

Alkyl Halide Reaction with Metallic Sodium

• When alkyl halides of lower alkanes are treated with metallic sodium, higher alkanes are formed. This reaction is known as the Wurtz reaction:

  2R-X + 2Na --> R-R + 2NaX

  The mechanism involves the formation of alkyl radicals, which then combine to form the higher alkane.

Reactivity of Alkyl Halides

• For a given alkyl group, the order of reactivity of alkyl halides follows the trend: RI > RBr > RCl > I.
• This decreasing reactivity is due to the decreasing strength of the C-halogen bond. As the halogen atom becomes larger and less electronegative, the bond length increases, and the bond strength decreases, making the molecule more susceptible to nucleophilic attack.

Conversion of Toluene To Benzyl Alcohol

• Toluene can be converted to benzyl alcohol by reacting it with KMnO4 or CrO3 in the presence of an appropriate solvent and acid:

  C6H5-CH3 + [O] (KMnO4 or CrO3) ---> C6H5-CH2OH

Conversion of Aniline to Chlorobenzene

• Aniline can be converted to chlorobenzene through a series of reactions involving diazotization and the Sandmeyer reaction. First, aniline is diazotized by reacting it with nitrous acid (NaNO2 / HCl) at low temperatures to form a diazonium salt. Subsequently, the diazonium salt is treated with CuCl in presence of HCl to form chlorobenzene.

  C6H5-NH2 + NaNO2 + HCl ---> C6H5-N2Cl + NaCl + 2H2O C6H5-N2Cl + CuCl ---> C6H5-Cl + N2 + CuCl2

Positive Tollen's Test

• Glucose and fructose give a positive Tollen's test. This is due to the presence of an aldehyde group in their open-chain structures.

Complete Hydrolysis of Cellulose

• The complete hydrolysis of cellulose yields D-glucose. Cellulose is a polysaccharide composed of repeating D-glucose units linked by β(1→4) glycosidic bonds.

Amino Acids with Phenolic-OH

• Tyrosine is the α-amino acid that has a phenolic-OH group as its side chain.

α-Amino Acids with Aromatic Side Chain

• Tyrosine contains an aromatic side chain.
• Tryptophan has an indole side chain.

Ketohexose

• Fructose is an example of a ketohexose.

Levorotatory

• Fructose is levorotatory.

Enzyme as Protein

• An enzyme is a protein.

Cause of Diabetes Mellitus

• Diabetes Mellitus is caused by the deficiency of insulin.

Isoelectric Point of Glycine

• The isoelectric point of glycine is 6.

Cause of Night Blindness

• Deficiency of vitamin A leads to night blindness.

Polymer of Nucleic Acid

• Nucleic acids are polymers of nucleotides.

Cause of Increased Blood Pressure

• Increased blood pressure may be caused by excess secretion of adrenaline.

Representation of Amino Acids

• Amino acids are best represented by their zwitterionic form.

Main Structural Feature of Protein

• The main structural feature of proteins is the peptide linkage.

Williamson's Reaction: Reagent and Equation

• In Williamson's reaction, an alkyl halide is treated with an alkoxide ion (RO-), which is usually prepared from an alcohol and a strong base like sodium hydroxide. This reaction yields an ether.

R-X + R'-ONa → R-O-R' + NaX

Complete the Reactions:

• (a) CH3CH2OH + PCl5 → CH3CH2Cl + POCl3 + HCl
• (b) CH3CH2Br + KOH (alc) → CH2=CH2 + KBr + H2O
• (c) CH3CH2-COOAg + Br2 → CH3CH2Br + CO2 + AgBr

Boiling Point of Alkyl Halides

• C2H5-I has the highest boiling point among C2H5-Cl, C2H5-Br, and C2H5-I. This is because iodine is the largest and most polarizable atom, leading to stronger London dispersion forces between the molecules.

SN2 Reaction in (CH3)3C- Cl and CH3Cl

• CH3Cl undergoes SN2 reaction and (CH3)3C-Cl undergoes SN1 reaction due to the steric hindrance present in (CH3)3C-Cl. SN2 reaction is favoured by less steric hindrance, whereas SN1 is favoured by more steric hindrance.

SN1 Mechanism in Tert.Butylbromide with Aq.KOH Solution:

• The SN1 reaction of tert-butyl bromide with aq. KOH is a two-step process:

  1. Formation of a carbocation: The tert-butyl bromide molecule undergoes ionization in the presence of the polar protic solvent (water) to form a carbocation ( (CH3)3C+ ) and a bromide ion (Br-). The carbocation is highly reactive due to its electron deficiency.
  2. Nucleophilic Attack: The hydroxide ion (OH-) from the aq. KOH solution acts as a nucleophile and attacks the carbocation. This results in the formation of tert-butanol ((CH3)3C-OH) as the final product.
  • The reaction can be represented as follows:

  (CH3)3C-Br + H2O --> (CH3)3C+ + Br- + H2O (CH3)3C+ + OH- --> (CH3)3C-OH