Explore the complete solutions and explanations for the Chemistry section of the UHS Entry Test 2011. Our detailed guide helps you understand key concepts and practice solved questions for successful exam preparation.
Q.45
In a mass spectrometer, the detector or collector measures the:
A) Masses of isotopes
B) Percentages of isotopes
C) Relative abundances of isotopes
D) Mass numbers of isotopes
Answer: C) Relative abundances of isotopes
Explanation: The mass spectrometer detects the relative abundances of isotopes by separating ions based on their mass-to-charge ratios. It measures how much of each isotope is present in a sample.
Q.46
How many chlorine atoms are in two moles of chlorine?
A) 2 x 6.02 x 10²³ atoms
B) 35.5 x 6.02 x 10²³ atoms
C) 2 x 10²³ atoms
D) 2 x 6.02 x 10²² atoms
Answer: A) 2 x 6.02 x 10²³ atoms
Explanation: One mole contains Avogadro’s number of atoms, which is 6.02 x 10²³. Therefore, 2 moles of chlorine will contain 2 x 6.02 x 10²³ atoms.
Q.47
Melting point of water is higher than petrol because intermolecular forces in water are:
A) Weaker than petrol
B) Stronger than petrol
C) Same as in petrol
D) Negligible
Answer: B) Stronger than petrol
Explanation: Water has hydrogen bonding, a very strong intermolecular force, whereas petrol has weaker London dispersion forces. These stronger forces in water lead to a higher melting point.
Q.48
DNA molecule is double-stranded, and in which two chains of DNA are twisted around each other by:
A) Hydrogen bonds
B) Van der Waals forces
C) Covalent bonds
D) Dative bonds
Answer: A) Hydrogen bonds
Explanation: Hydrogen bonds between complementary nitrogenous bases in the DNA strands hold the two strands together, forming a double helix.
Q.49
The elements for which the value of ionization energy is low can:
A) Gain electrons readily
B) Gain electrons with difficulty
C) Lose electrons less readily
D) Lose electrons readily
Answer: D) Lose electrons readily
Explanation: Elements with low ionization energy can easily lose electrons because less energy is required to remove electrons from the atom.
Q.50
The nature of cathode rays in a discharge tube:
A) Depends on the nature of gas taken in the discharge tube
B) Depends upon the nature of cathode in discharge tube
C) Is independent of the nature of the gas in discharge tube
D) Depends upon the nature of anode in the discharge tube
Answer: C) Is independent of the nature of the gas in the discharge tube
Explanation: Cathode rays consist of electrons, which are the same regardless of the type of gas present in the discharge tube.
Q.51
The ability of an atom in a covalent bond to attract the bonding electrons is called:
A) Ionization energy
B) Ionic bond energy
C) Electronegativity
D) Electron affinity
Answer: C) Electronegativity
Explanation: Electronegativity is the ability of an atom to attract bonding electrons in a covalent bond.
Q.52
The paramagnetic character of a substance is due to:
A) Bond pairs of electrons
B) Lone pairs of electrons
C) Unpaired electrons in atom or molecule
D) Paired electrons in valence shells of electrons
Answer: C) Unpaired electrons in atom or molecule
Explanation: Paramagnetism occurs due to the presence of unpaired electrons that align with a magnetic field.
Q.53
Lattice energy of an ionic crystal is the enthalpy of:
A) Combustion
B) Dissociation
C) Dissolution
D) Formation
Answer: D) Formation
Explanation: Lattice energy refers to the energy released when gaseous ions form an ionic solid, so it is associated with the formation of the crystal.
Q.54
In standard enthalpy of atomization, heat of the surrounding:
A) Remains unchanged
B) Increases
C) Decreases
D) Increases then decreases
Answer: B) Increases
Explanation: During atomization, energy is absorbed to break bonds, which leads to an increase in the heat of the surroundings.
Q.55
Mole fraction of any compound is the ratio of moles of all components in a:
A) Compound
B) Solution
C) Molecule
D) Solid
Answer: B) Solution
Explanation: Mole fraction is calculated in solutions, not compounds or molecules.
Q.56
Molarity is defined as the number of moles of any substance dissolved:
A) Per dm³ of solution
B) Per m³ of solution
C) Per 100 ml of solution
D) In one gram of solution
Answer: A) Per dm³ of solution
Explanation: Molarity is defined as moles of solute per liter (dm³) of solution.
Q.57
In an electrolytic cell, a salt bridge is used in order to:
A) Pass the electric current
B) Prevent the flow of ions
C) Mix solutions of two half cells
D) Allow movement of ions between two half cells
Answer: D) Allow movement of ions between two half cells
Explanation: The salt bridge allows ions to move between half cells, maintaining electrical neutrality in the system.
Q.58
In all oxidation reactions, atoms of an element in a chemical species lose electrons and increase their:
A) Oxidation states
B) Reductions
C) Electrode
D) Negative charges
Answer: A) Oxidation states
Explanation: Oxidation involves the loss of electrons, which results in an increase in oxidation state.
Q.59
In “AgCl solution, some salt of NaCl is added, “AgCl will be precipitated due to:
A) Solubility
B) Electrolyte
C) Unsaturation effect
D) Common ion effect
Answer: D) Common ion effect
Explanation: The addition of NaCl increases the concentration of Cl⁻ ions, causing AgCl to precipitate due to the common ion effect.
Q.60
When ‘Ka’ for an acid is higher, the stronger is the acid; relate the strength of an acid with ‘pKa’:
A) Higher pKa, weaker the acid
B) Lower pKa, stronger the acid
C) pKa has no relation with acid strength
D) Both A and B
Answer: B) Lower pKa, stronger the acid
Explanation: A lower pKa value indicates a stronger acid because it corresponds to a higher Ka, meaning the acid dissociates more readily.
Q.61
It is experimentally found that a catalyst is used to:
A) Lower the activation energy
B) Increase the activation energy
C) Lower the pH
D) Decrease the temperature of the reaction
Answer: A) Lower the activation energy
Explanation: Catalysts work by lowering the activation energy, making the reaction occur more easily and faster.
Q.62
According to the collision theory of bimolecular reactions in the gas phase, the minimum amount of energy required for an effective collision is known as:
A) Heat of reaction
B) Rate of reaction
C) Has no effect on the reaction
D) Energy of activation
Answer: D) Energy of activation
Explanation: The energy of activation is the minimum energy needed for molecules to collide effectively and react.
Q.63
Diamond is a non-conductor, whereas graphite is a good conductor because:
A) Graphite has a layered structure
B) Graphite has free electrons that can move
C) In graphite, all valence electrons are tetrahedrally bound
D) Graphite is soft and greasy
Answer: B) Graphite has free electrons that can move
Explanation: In graphite, one valence electron from each carbon atom is free to move, which makes graphite a good conductor of electricity.
Q.64
The diagram below is a plot of melting points of elements of the second period against their atomic numbers. Lithium and fluorine are placed at the extreme ends of the plot, on the basis of melting points where will you place Carbon?
A) 1
B) 2
C) 3
D) 4
Answer: D) 3
Explanation: Carbon has a relatively high melting point due to its strong covalent bonds (diamond), so it is placed at position 3.
Q.65
When elements of Group II-A (alkaline earth metals) are exposed to air, they quickly become coated with a layer of oxide. What is the purpose of this oxide layer?
A) The oxide layer exposes the metal to atmospheric attack
B) The oxide layer increases the reactivity of metal
C) The oxide layer protects the metal from further atmospheric attack
D) The oxide layer gives the metal a shiny silvery appearance
**Answer: C) The oxide layer protects the metal from
further atmospheric attack**
Explanation: The oxide layer forms a protective barrier preventing further corrosion of the metal.
Q.66
In silicon dioxide, each silicon atom is tetrahedrally bonded to four oxygen atoms, and each oxygen atom is bonded to two silicon atoms. The ratio of silicon to oxygen atoms is:
A) 1:1
B) 2:1
C) 1:2
D) 1:3
Answer: C) 1:2
Explanation: The empirical formula for silicon dioxide is SiO₂, meaning one silicon atom for every two oxygen atoms.
Q.67
Hydrogenation of unsaturated oils is done by using:
A) Finely divided nickel
B) Finely divided platinum
C) Heat
D) Hydrogen gas
Answer: A) Finely divided nickel
Explanation: Finely divided nickel is commonly used as a catalyst in the hydrogenation of unsaturated oils.
Q.68
Pick the correct statement:
A) Chelates are usually more stable than ordinary complexes
B) Chelates are usually less stable than ordinary complexes
C) Chelates do not form complexes
D) Chelates and ordinary complexes are equally stable
Answer: A) Chelates are usually more stable than ordinary complexes
Explanation: Chelates form multiple bonds with a metal ion, making them more stable than complexes formed by single bonds.
Q.69
In the contact process, the catalyst used for the conversion of sulfur dioxide to sulfur trioxide is:
A) Zinc oxide
B) Iron oxide
C) Vanadium pentoxide
D) Aluminum oxide
Answer: C) Vanadium pentoxide
Explanation: Vanadium pentoxide (V₂O₅) is the catalyst used in the contact process for the conversion of sulfur dioxide to sulfur trioxide.
Q.70
The unpolluted natural rainwater is slightly acidic due to the reaction of rainwater with:
A) Sulphur dioxide
B) Oxides of nitrogen
C) Carbon dioxide
D) Hydrogen present in air
Answer: C) Carbon dioxide
Explanation: Natural rainwater is slightly acidic due to the dissolution of carbon dioxide from the atmosphere, which reacts with water to form carbonic acid (H₂CO₃).
Q.71
In the Haber’s process for the manufacturing of ammonia, nitrogen is taken from:
A) Proteins occurring in living bodies
B) Ammonium salts obtained industrially
C) Air
D) Mineral containing nitrates
Answer: C) Air
Explanation: In the Haber process, nitrogen is taken from the air, where it is present as N₂ gas, and combined with hydrogen to form ammonia (NH₃).
Q.72
In comparison with oxygen gas, a strong triple bond is present between two nitrogen atoms in a molecule and therefore nitrogen gas is:
A) Highly reactive gas
B) Completely inert like noble gases
C) Very less reactive gas
D) Moderately reactive gas
Answer: C) Very less reactive gas
Explanation: Nitrogen gas (N₂) has a strong triple bond between the nitrogen atoms, making it quite stable and less reactive compared to oxygen gas.
Q.73
The compound with an atom, which has an unshared pair of electrons, is called:
A) Nucleophile
B) Electrophile
C) Protophile
D) None of the above
Answer: A) Nucleophile
Explanation: A nucleophile is a species that has an unshared pair of electrons and can donate these electrons to an electrophile in a chemical reaction.
Q.74
1-chloropropane and 2-chloropropane are isomers of each other; the type of isomerism in these two is called:
A) Chain isomerism
B) Cis-trans isomerism
C) Position isomerism
D) Functional group isomerism
Answer: C) Position isomerism
Explanation: 1-chloropropane and 2-chloropropane are position isomers because the chlorine atom is attached to different carbon atoms in each molecule.
Q.75
Benzene, in the presence of AlCl₃, produces acetophenone when it reacts with:
A) Acetyl chloride
B) Acetic acid
C) Ethylbenzene
D) Ethanoic acid
Answer: A) Acetyl chloride
Explanation: In the presence of AlCl₃ (a Lewis acid), benzene reacts with acetyl chloride (CH₃COCl) to form acetophenone (C₆H₅COCH₃) via an electrophilic aromatic substitution reaction.
Q.76
The substitution of a “-H” by “-NO₂” group in benzene is called:
A) Nitration
B) Amination
C) Sulphonation
D) Reduction of benzene
Answer: A) Nitration
Explanation: The substitution of a -NO₂ (nitro) group for a hydrogen atom in benzene is known as nitration. This reaction typically involves nitric acid (HNO₃) in the presence of a catalyst like sulfuric acid (H₂SO₄).
Q.77
When a purely alcoholic solution of sodium/potassium hydroxide and halogenoalkanes are reacted, an alkene is formed. What is the mechanism of reaction?
A) Elimination
B) Dehydration
C) Substitution
D) Addition
Answer: A) Elimination
Explanation: When sodium or potassium hydroxide reacts with halogenoalkanes in alcoholic solution, an elimination reaction occurs, leading to the formation of an alkene by the removal of HX (hydrogen halide).
Q.78
The organic compound carbon tetrachloride is used as:
A) Lubricant
B) Solvent
C) Oxidant
D) Plastic
Answer: B) Solvent
Explanation: Carbon tetrachloride (CCl₄) is commonly used as a solvent in various industrial applications due to its ability to dissolve oils, fats, and other non-polar substances.
Q.79
An alcohol is converted to an aldehyde with the same number of carbon atoms as that of the alcohol in the presence of K₂Cr₂O₇/H₂SO₄. The alcohol is:
A) CH₃CH₂OH
B) CH₃CH₂CH₂OH
C) (CH₃)₂CHOH
D) (CH₃)₃COH
Answer: A) CH₃CH₂OH
Explanation: Ethanol (CH₃CH₂OH) is oxidized to acetaldehyde (CH₃CHO) by potassium dichromate (K₂Cr₂O₇) in the presence of sulfuric acid (H₂SO₄).
Q.80
Which of the following is a secondary alcohol?
A) CH₃OH
B) CH₃CH₂OH
C) (CH₃)₂CHOH
D) (CH₃)₃COH
Answer: C) (CH₃)₂CHOH
Explanation: A secondary alcohol has the hydroxyl group (-OH) attached to a carbon atom that is connected to two other carbon atoms. (CH₃)₂CHOH is a secondary alcohol.
Q.81
Which enzyme is involved in the fermentation of glucose?
A) Zymase
B) Invertase
C) Urease
D) Diastase
Answer: A) Zymase
Explanation: Zymase is the enzyme complex responsible for fermenting glucose into alcohol (ethanol) and carbon dioxide in yeast.
Q.82
Relative acidic strength of alcohol, phenol, water, and carboxylic acid is:
A) Carboxylic acid > Alcohol > Phenol > Water
B) Carboxylic acid > Phenol > Water > Alcohol
C) Phenol > Carboxylic acid > Alcohol > Water
D) Water > Alcohol > Phenol > Carboxylic acid
Answer: A) Carboxylic acid > Alcohol > Phenol > Water
Explanation: Carboxylic acids are the most acidic due to the resonance stabilization of their conjugate base. Alcohols are weaker acids, followed by phenols, and water is the least acidic of the four.
Q.83
Consider the following reaction:
R-CHO + 2[Ag(NH₃)₂]OH →
This reaction represents one of the following tests:
A) Fehling test
B) Benedict test
C) Ninhydrin test
D) Tollens test
Answer: D) Tollens test
Explanation: This reaction is the Tollens test, used to detect aldehydes. Tollens’ reagent, which contains silver(I) ions complexed with ammonia, reacts with aldehydes to produce a silver mirror on the test tube.
Q.84
In the below reaction, the nucleophile is:
HCHO + HCN → R-COONH₄ + 2Ag + 2NH₃ + H₂O
A) CN⁻
B) NH₃
C) OH⁻
D) H₂O
Answer: A) CN⁻
Explanation: In this reaction, cyanide ion (CN⁻) is the nucleophile that attacks the carbonyl carbon of formaldehyde (HCHO) to form the product.
Q.85
Which one of the following compounds belongs to the homologous series of aldehydes?
A) HO
B) -NH₂
C) CH₃COOH
D) HCHO
Answer: D) HCHO
Explanation: HCHO (formaldehyde) is an aldehyde. The other compounds are either carboxylic acids (CH₃COOH) or amines (-NH₂).
Q.86
The products of the following reaction are:
CH₃COOH + PCl₅ →
A) CH₃COCl + POCl₃ + H₂O
B) CH₃COCl + POCl₃ + HCl
C) CH₃COCl + PCl₃ + H₂O
D) CH₃COCl + PCl₄ + HCl
Answer: A) CH₃COCl + POCl₃ + H₂O
Explanation: When acetic acid (CH₃COOH) reacts with phosphorus pentachloride (PCl₅), it forms acetyl chloride (CH₃COCl), phosphorus oxychloride (POCl₃), and water (H₂O).
Q.87
In the above reaction, A and B are:
CH₃COOH + Mg →
A) Acetic acid and acid amide
B) Acetic acid and ammonia
C) Acetic acid and methyl chloride
D) Acetic acid and ammonium chloride
Answer: B) Acetic acid and ammonia
Explanation: When acetic acid reacts with magnesium, it forms magnesium acetate (Mg(CH₃COO)₂) and releases hydrogen gas. Magnesium may react with water to form ammonia in some conditions.
Q.88
Consider the following reaction:
CH₃COOH + Mg (metal) →
What product will form?
A) Magnesium formate
B) Magnesium acetate
C) Magnesium ion
D) Carboxylate ion
Answer: B) Magnesium acetate
Explanation: When acetic acid reacts with magnesium, the product formed is magnesium acetate (Mg(CH₃COO)₂), and magnesium hydroxide may also be produced if water is involved.
Q.89
The -NH-CO- group is called:
A) Amide group
B) Amino group
C) Ester group
D) Peptide linkage
Answer: A) Amide group
Explanation: The -NH-CO- group is called an amide group, which is found in amides and peptide bonds.
Q.90
Which one of the following is an alpha amino acid?
A) NH₂-CH-COOH
B) NH₂-CH₂-COOH
C) NH₂-CH₂-CH₂-COOH
D) HOOC-CH₂-CH₂-COOH
Answer: C) NH₂-CH₂-CH₂-COOH
Explanation: Alpha amino acids have the amino group (-NH₂) attached to the alpha (α)-carbon, which is the carbon adjacent to the carboxyl group (-COOH). The compound NH₂-CH₂-CH₂-COOH is an example of an alpha amino acid.
Q.91
Which of the following has an amino R-group?
A) Lysine
B) Proline
C) Valine
D) Alanine
Answer: A) Lysine
Explanation: Lysine has an amino group (-NH₂) attached to its side chain (R group). The other amino acids listed do not have an amino group in their side chains.
Q.92
At intermediate pH, amino acids form Zwitterions containing:
A) -NH₃⁺ and COO⁻
B) -NH₂ and COO⁻
C) -NH₂ and COCH₃
D) -NH₂ and COOH
Answer: A) -NH₃⁺ and COO⁻
Explanation: At intermediate pH (near the isoelectric point), amino acids exist as zwitterions, with a positively charged amino group (-NH₃⁺) and a negatively charged carboxyl group (COO⁻).
Q.93
When hexane dioic acid is heated with hexamethylenediamine, the compound formed is:
A) Polypeptide
B) Addition polymer
C) Ester
D) Nylon 6,6
Answer: D) Nylon 6,6
Explanation: Hexane dioic acid (adipic acid) and hexamethylenediamine react to form Nylon 6,6, which is a type of polyamide (a polymer linked by amide bonds).
Q.94
A polymer in which the number of amino acid residues is greater than 100 or molecular mass is greater than 1000, is known as:
A) Protein
B) Polypeptide
C) Dipeptide
D) Tripeptide
Answer: A) Protein
Explanation: A polymer with more than 100 amino acid residues and a molecular mass greater than 1000 is considered a protein. A polypeptide refers to a shorter chain, typically with fewer than 100 amino acids.
Q.95
Aspartic acid is an acidic amino acid, which has the chemical formula:
A) NH₂-CH₂-CH₂-COOH
B) NH₂-CH-CH₂-COOH
C) NH₂-CH₂-COOH
D) NH₂-C-COOH
Answer: A) NH₂-CH₂-CH₂-COOH
Explanation: Aspartic acid has the chemical formula C₄H₇NO₄. It is an acidic amino acid, and its structure includes a carboxyl group (-COOH) in the side chain, which makes it acidic.
Q.96
Glucose and fructose are common examples of:
A) Pentoses
B) Hexoses
C) Heptoses
D) Butoses
Answer: B) Hexoses
Explanation: Both glucose and fructose are hexoses, meaning they are six-carbon sugars. Pentoses have five carbon atoms, heptoses have seven, and butoses have four.
Q.97
The reaction between fats and caustic soda is called:
A) Hydrogenolysis
B) Fermentation
C) Carboxylation
D) Saponification
Answer: D) Saponification
Explanation: Saponification is the chemical reaction between fats (or oils) and a strong base like caustic soda (sodium hydroxide), resulting in the formation of glycerol (glycerin) and soap (fatty acid salts).
Q.98
Macromolecules are described as large molecules built up from small repeating units known as:
A) Monomers
B) Isomers
C) Metameres
D) Tautomer
Answer: A) Monomers
Explanation: Macromolecules, such as polymers, are made up of repeating structural units called monomers. Isomers, metameres, and tautomers are different types of compounds based on structural variations but are not related to macromolecular structure.
Q.99
Polyvinyl chloride is an example of:
A) Addition polymer
B) Condensation polymer
C) Biopolymer
D) Thermosetting polymer
Answer: A) Addition polymer
Explanation: Polyvinyl chloride (PVC) is a type of addition polymer, where monomers (vinyl chloride) are added together without the elimination of any small molecules (like water).
Q.100
Terylene, a polyester, is an example of:
A) Addition polymer
B) Condensation polymer
C) Biopolymer
D) Thermosetting polymer
Answer: B) Condensation polymer
Explanation: Terylene (also known as PET or polyethylene terephthalate) is a polyester formed through condensation polymerization, where water is eliminated during the formation of the polymer.
Q.101
The suspected liver carcinogen, which also has negative reproductive and developmental effects on humans, is:
A) Chloroform
B) Bromoform
C) Tropoform
D) Todoform
Answer: A) Chloroform
Explanation: Chloroform is a suspected liver carcinogen and has been shown to cause negative reproductive and developmental effects in humans. The other options are not known to have these effects.
Q.102
Peroxyacetyl nitrate is an irritant to human beings, and it affects:
A) Nose
B) Stomach
C) Ears
D) Eyes
Answer: D) Eyes
Explanation: Peroxyacetyl nitrate (PAN) is a pollutant that can irritate the eyes, as well as the respiratory system, causing discomfort and damage in high concentrations.
