Solid State
1. Solid-state is denser than the liquid and gaseous states of the same substance. Which of the following is an exception to this rule?
a) Mercury
b) Carbon dioxide (dry ice)
c) Ice
d) NaCl
View Answer
Explanation: The density of ice is about 0.92 g/cm3 while that of water is 1 g/cm3. Mercury has density 14.184 g/cm3 as solid and 13.69 g/cm3 as liquid. Carbon dioxide has density 1.56 g/cm3 as solid and 1.10 g/cm3 as liquid. NaCl has density 2.71 g/cm3 as solid and 1.556 g/cm3 in molten state. Therefore only ice has lesser density as a solid than as a liquid.
2. Which of the following can be used to describe a crystalline solid?
a) Heterogeneous, anisotropic
b) Homogeneous, anisotropic
c) Heterogeneous, isotropic
d) Homogeneous, isotropic
View Answer
Explanation: Homogeneity refers to uniformity in composition, which is a characteristic property of crystalline solids. Isotropy is when the values of physical properties do not change with direction throughout the body of the solid. Crystalline solids are anisotropic because the composition of the solid changes with direction, hence the physical properties also change with direction.
3. When a single substance can crystallize in two or more forms under different conditions provided, it is called as _________
a) Polymorphous
b) Isomorphous
c) Semimorphous
d) Multimorphous
View Answer
Explanation: Isomorphous is when two or more substances have the same crystal structure. Polymorphous is when a single substance can crystallize in two or more forms depending upon the conditions.
4. Which of the following is an amorphous solid?
a) Quartz
b) Quartz glass
c) Graphite
d) Salt (NaCl)
View Answer
Explanation: Quartz glass does not have a perfectly ordered structure, hence it is classified as an amorphous solid. The rest are crystalline solids due to ordered structures.
5. Amorphous solids are actually supercooled liquids.
a) True
b) False
View Answer
Explanation: Amorphous solids behave like fluids and flow very slowly under the influence of gravity. Hence, they are said to be supercooled liquids.
6. Which type of solid structure melts at a definite, sharp melting point?
a) All types of solids
b) No type of solid
c) Amorphous solids
d) Crystalline solids
View Answer
Explanation: Crystalline solids have a perfectly ordered structure which collapses immediately at a specific temperature. Amorphous solids melt over a range of temperatures, not one specific value.
7. Which of the following describes a general solid?
a) Compressible
b) Incompressible
c) Fluid
d) Semi-compressible
View Answer
Explanation: The intermolecular forces of attraction in a solid are very strong, making it incompressible. Gases are highly compressible, while liquids are semi-compressible. Fluid is a property of a substance that can ‘flow’.
8. _________ is the basic repeated structural unit of a crystalline solid.
a) Monomer
b) Molecule
c) Unit cell
d) Atom
View Answer
Explanation: Crystalline solids are composed of many small crystals, each of which is called a unit cell. It is a specific term. Monomer is the basic unit for a polymer, and atoms make up molecules, which can further arrange themselves to form solids, liquids or gases.
9. Which of the following statements is true for an amorphous solid?
a) Long range order is present
b) Short range order is present
c) There is no orderly arrangement
d) Complete order is present at lower temperatures
View Answer
Explanation: For an amorphous solid there is short range order present which is independent of the temperature. Long range order is present in crystalline solids.
10. Sulfur exists in two polymorphic forms ____________ and ______________
a) rhombic and monoclinic
b) rhombic and triclinic
c) hexagonal and triclinic
d) hexagonal and monoclinic
View Answer
Explanation: There are two polymorphous structures of sulfur, rhombic and monoclinic. Polymorphous structures occur when a single substance can crystallize in two or more forms depending upon the conditions.
Solutions
1. Which of the following is not a solid solution?
a) Brass
b) Bronze
c) Hydrated salts
d) Aerated drinks
View Answer
Explanation: A solid solution is a solid-state solution of one or more solutes in a solvent. Brass, bronze, and hydrated salts are examples of solid solutions. Aerated drinks are examples of liquid solutions (gas in liquid).
2. The solution of mercury with other metals is called amalgam.
a) True
b) False
View Answer
Explanation: Alloys of mercury with other metals are called amalgams. An alloy is a type of solid solution (solid in solid). Some important amalgams are zinc amalgam, potassium amalgam, sodium amalgam, aluminium amalgam, and tin amalgam.
3. What is an alloy of copper and zinc called?
a) Bronze
b) German silver
c) Brass
d) Solder
View Answer
Explanation: An alloy of copper and zinc is called Brass. German silver is an alloy of copper, zinc and nickel, sometimes also containing lead and tin. Bronze is an alloy of copper and tin. Solder is an alloy of tin, lead and antimony.
4. What is camphor in N2 gas an example of?
a) Solid in liquid solution
b) Liquid in gas solution
c) Solid in gas solution
d) Gas in gas solution
View Answer
Explanation: Camphor in N2 gas is an example of solid in gas gaseous solution. A solution in which the solvent is gaseous is called gaseous solution. Some other examples of gaseous solutions are air (O2 + N2), Iodine vapours in air, humidity in air, etc.
5. Which of the following is not a copper alloy?
a) Bronze
b) Stainless steel
c) Brass
d) Gunmetal
View Answer
Explanation: Bronze is an alloy of copper and tin. Stainless steel is an alloy of iron with chromium. It also contains varying amounts of carbon, silicon and manganese. Brass is an alloy of copper and zinc. Gunmetal is an alloy of copper, tin and zinc.
6. A supersaturated solution is not a metastable solution.
a) True
b) False
View Answer
Explanation: A metastable solution is one which is stable when undisturbed but is capable of reaction if disturbed. Supersaturated solutions are stable when undisturbed and precipitates out crystals of the solute when disturbed. Hence, supersaturated solutions are metastable.
7. Which of the following is a true solution?
a) Salt solution
b) Ink
c) Blood
d) Starch solution
View Answer
Explanation: A true solution is a homogeneous mixture of two or more materials with a particle size of less than 10-9 m or 1 nm dissolved in the solvent. Ink, blood and starch solution are colloidal solutions. A simple solution of salt in water is a true solution.
8. What type of solution is Cranberry glass?
a) Emulsion
b) Solid sol
c) Solid aerosol
d) Gel
View Answer
Explanation: Emulsion, solid sol, solid aerosol and gel are types of colloidal solutions. Cranberry glass is formed by the addition of a solid solute to a solid solvent(gold salts and glass respectively). Hence, it is a Solid sol.
9. What is pumice stone an example of?
a) Solid aerosol
b) Emulsion
c) Liquid aerosol
d) Solid foam
View Answer
Explanation: There are 8 types of colloidal solutions namely solid sol, sol, solid aerosol, gel, emulsion, liquid aerosol, solid foam and foam. Pumice stone is a gas in solid type colloidal solution, i.e., solid foam.
10. What is the observation on adding a solute crystal to a supersaturated solution?
a) It becomes a colloidal solution
b) The solute dissolves in the solution
c) The solution desaturates
d) The solute precipitates out of the solution
View Answer
Explanation: When a solute crystal is added to a supersaturated solution, solute particles leave the solution and forms a crystalline precipitate. The addition of the solute crystal is also called seeding.
Electrochemistry
1. An electrochemical cell can only convert electrical energy to chemical energy.
a) True
b) False
View Answer
Explanation: An electrochemical cell can convert electrical energy to chemical energy and can also convert electrical energy to chemical energy. There are two types of electrochemical cells- Galvanic cell and Electrolytic cell.
2. An electrochemical cell generally consists of a cathode and an anode. Which of the following statements is correct with respect to the cathode?
a) Oxidation occurs at the cathode
b) Electrons move into the cathode
c) Usually denoted by a negative sign
d) Is usually made up of insulating material
View Answer
Explanation: Cathodes are usually metal electrodes. It is the electrode where reduction takes place. The cathode is the positive electrode in a galvanic cell and a negative electrode in an electrolytic cell. Electrons move into the cathode.
3. When equilibrium is reached inside the two half-cells of the electrochemical cells, what is the net voltage across the electrodes?
a) > 1
b) < 1
c) = 0
d) Not defined
View Answer
Explanation: A half-cell is half of an electrochemical cell (electrolytic or galvanic), where either oxidation or reduction occurs. At equilibrium, there is no transfer of electrons across the half cells. Therefore, the potential difference between them is nil.
4. Which of the following is not a generally used electrolyte in the salt bridges used to connect the two half-cells of an electrochemical cell?
a) NaCl
b) KNO3
c) KCl
d) ZnSO4
View Answer
Explanation: A salt bridge is a device used to connect the oxidation and reduction half-cells of a galvanic cell (a type of electrochemical cell). Strong electrolytes are generally used to make the salt bridges in electrochemical cells. Since ZnSO4 is not a strong electrolyte, it is not used to make salt bridges.
5. When no current is drawn through an electrochemical cell, the difference of the electrode potentials of the two electrodes is called cell emf. True or False?
a) True
b) False
View Answer
Explanation: Emf of a cell is equal to the maximum potential difference across its electrodes, which occurs when no current is drawn through the cell. It can also be defined as the net voltage between the oxidation and reduction half-reactions.
a) Cell potential is an extensive property
b) Cell potential is an intensive property
c) The Gibbs free energy of an electrochemical cell is an intensive property
d) Gibbs free energy is undefined for an electrochemical cell
View Answer
Explanation: Cell potential is an intensive property as it is independent of the amount of material present. Gibbs free energy is defined for an electrochemical cell and is an extensive property as it depends on the quantity of the material.
7. Which of the following factors does not affect the electrode potential of an electrode?
a) Nature of the electrode (metal)
b) Temperature of the solution
c) Molarity of the solution
d) Size of the electrode
View Answer
Explanation: Electrode potential is the tendency of an electrode to accept or to lose electrons. Electrode potential depends on the nature of the electrode, temperature of the solution and the concentration of metal ions in the solution. It doesn’t depend on the size of the electrode.
8. Why are the saturated solutions of electrolytes for the salt bridge prepared in agar-agar jelly or gelatin?
a) The jelly acts as an electrolyte
b) It helps the electrolytes to mix with the contents of the half cells
c) It helps maintain the electrical polarity between the two half-cell solutions
d) It keeps the electrolyte in semi-solid phase and prevents it from mixing with the two half-cell solutions
View Answer
Explanation: The salt bridge connects the two half-cell solutions to complete the circuit of the electrochemical cell. The electrolytes of the salt bridge are generally prepared in agar-agar or gelatin so that the electrolytes are kept in a semi-solid phase and do not mix with the half-cell solutions and interfere with the electrochemical reaction.
9. Which of the following is not a characteristic feature of a salt bridge?
a) Salt bridge joins the two halves of an electrochemical cell
b) It completes the inner circuit
c) It is filled with a salt solution (or gel)
d) It does not maintain electrical neutrality of the electrolytic solutions of the half-cells
View Answer
Explanation: A salt bridge is a junction that connects the anodic and cathodic compartments in a cell or electrolytic solution. It maintains electrical neutrality within the internal circuit, preventing the cell from rapidly running its reaction to equilibrium.
10. Which of the following is not a type of electrochemical cell?
a) Voltaic cell
b) Photovoltaic cell
c) Electrolytic cell
d) Fuel Cell
View Answer
Explanation: A Voltaic or Galvanic cell is a type of electrochemical cell that converts chemical energy into electrical energy. Photovoltaic cells are used to convert light energy into electrical energy. An Electrolytic cell is a type of electrochemical cell that converts electrical energy into chemical energy. A fuel cell is an electrochemical cell that converts the chemical energy of a fuel and an oxidizing agent into electricity.
11. What is the direction of flow of electrons in an electrolytic cell?
a) Anode to cathode externally
b) Anode to cathode internally
c) Cathode to anode externally
d) Cathode to anode in the solution
View Answer
Explanation: An electrolytic cell is a type of electrochemical cell. An electrolytic cell converts electrical energy into chemical energy. Electrons flow from anode to cathode through the external supply in an electrolytic cell. In the solution, only ions flow and not the electrons.
12. Which of the following is a not a secondary cell?
a) Nickel-cadmium cell
b) Lead storage cell
c) Mercury cell
d) Leclanche cell
View Answer
Explanation: A secondary battery (a series of cells) is one which can be charged, discharged into a load, and recharged many times. Nickel-cadmium cell, Lead storage cell and Mercury cell are examples of secondary cells. Leclanche cell is an example of a primary cell.
13. Which of the following statements regarding primary cells is false?
a) Primary cells cannot be recharged
b) They have low internal resistance
c) They have an irreversible chemical reaction
d) Their initial cost is cheap
View Answer
Explanation: Primary cells cannot be used again and again. Since there is no fluid inside, these cells are also known as dry cells. The internal resistance is high and the chemical reaction is irreversible. Their initial cost is cheap.
14. What is the observation when the opposing external applied potential to an electrochemical cell is greater than the cell’s potential?
a) The electrochemical cell behaves like an electrolytic cell
b) The electrochemical cell stops functioning
c) Only oxidation reactions occur in the cell
d) Only reduction reactions occur in the cell
View Answer
Explanation: In an electrochemical cell, when an opposing externally potential is applied and increased slowly, the reaction continues to take place. When the external potential is equal to the potential of the cell, the reaction stops. Once the externally applied potential is greater than the potential of the cell, the reaction goes in the opposite direction and the cell behaves like an electrolytic cell.
15. Which of the following conditions are satisfied when the cell reaction in the electrochemical cell is spontaneous?
a) ΔG° > 0
b) E°cell < 0
c) E°cell = 0
d) ΔG° < 0
View Answer
Explanation: For all spontaneous chemical reactions, the change in Gibbs free energy (ΔG°) is always negative. For a spontaneous reaction in an electrolytic cell, the cell potential (E°cell) should be positive.
Chemical Kinetics
1. For a second-order reaction, what is the unit of the rate of the reaction?
a) s-1
b) mol L-1s-1
c) mol-1 L s-1
d) mol-2 L2 s-1
View Answer
Explanation: The unit of the rate of the reaction (k) is (mol L-1) 1-n s-1, where n is the order of the reaction.
For a second-order reaction, n=2
(mol L-1) 1-n s-1 = (mol L-1)1-2 s-1 = mol-1 L s-1.
2. The rate constant of a reaction is k=3.28 × 10-4 s-1. Find the order of the reaction.
a) Zero order
b) First order
c) Second order
d) Third order
View Answer
Explanation: Given,
k= 3.28 × 10-4 s-1
The general formula to find the units for rate constant, k=(mol L-1)1-ns-1 where n is the order of the reaction. The value of n must be 1 for (mol L-1)1-ns-1 to become s-1. Therefore, k=3.28 × 10-4s-1 represents a first order reaction.
3. For a reaction A +B → C, the experimental rate law is found to be R=k[A]1[B]1/2. Find the rate of the reaction when [A] = 0.5 M, [B] = 0.1 M and k=0.03.
a) 4.74 × 10-2 (L/mol)1/2 s-1
b) 5.38 × 10-2 (L/mol)1/2 s-1
c) 5.748 × 10-2 (L/mol)1/2 s-1
d) 4.86 × 10-2 (L/mol)1/2 s-1
View Answer
Explanation: Given, [A] = 0.5 M, [B] = 0.1 M and k= 0.03
From the rate law it is evident that the order of the reaction is 1+ 0.5 = 1.5 =
Therefore the unit of k= (mol L-1)1-1.5 s-1 = (L/mol)1/2 s-1
R= k[A]1[B]1/2 = 0.03 × 0.5 × 0.11/2 = 4.74 × 10-2(L/mol)1/2 s-1.
4. The reaction NO2 + CO → NO + CO2 takes place in two steps. Find the rate law.
2NO2 → NO + NO3 (k1) – slow
NO3 + CO → CO2 + NO2 (k2) – fast
a) R = k1 [NO2]3
b) R = k2 [NO3] [CO]
c) R = k1 [NO2]
d) R = k1 [NO2]2
View Answer
Explanation: In any reaction the slowest step is the rate determining step, the rate of the overall reaction depends on this step. So, 2NO2 → NO + NO3(k1) is the rate determining step. Therefore the rate law R= k1[NO2]2.
5. For the reaction A + H2O → products, find the rate of the reaction when [A] = 0.75 M, k= 0.02.
a) 0.077 s-1
b) 0.085 s-1
c) 0.015 s-1
d) 0.026 s-1
View Answer
Explanation: Given,
[A] = 0.75 M, k= 0.02
The reaction belongs to pseudo first order reaction so, the unit is s-1
R= k [A]= 0.02 × 0.75= 0.015 s-1.
6. What is the rate law for acid hydrolysis of an ester such as CH3COOC2H5 in aqueous solution?
a) k [CH3COOC2H5]
b) k [CH3COOC2H5] [H2O]
c) k [CH3COOC2H5]2
d) k
View Answer
Explanation: Acid hydrolysis of ester, CH3COOC2H5 + H2O → CH3COOH + C2H5OH
The order of the reaction may be altered sometimes by taking reactant in excess compared to the other.
The rate law R= k [CH3COOC2H5] [H2O] however water is present in excess.
So, R= k [CH3COOC2H5].
7. What is the concentration of the reactant in a first order reaction when the rate of the reaction is 0.6 s-1 and the rate constant is 0.035?
a) 26.667 M
b) 17.143 M
c) 26.183 M
d) 17.667 M
View Answer
Explanation: Given, R=0.6 s-1 and k= 0.035
For a first order reaction R= k [A]
[A]=
8. How many times will the rate of the elementary reaction 3X + Y → X2Y change if the concentration of the substance X is doubled and that of Y is halved?
a) r2= 4.5r1
b) r2= 5r1
c) r2= 2r1
d) r2= 4r1
View Answer
Explanation: Since it is an elementary reaction, its rate law r1= k [A] 3[B]
When the concentrations are changed the new rate will be r2= k (2[A])3([B]/2) = 4k[A]3[B]
So, r2=4r1.
9. What is the rate law for the reaction C2H4 + I2 → C2H4I2?
a) R= [C2H4] [I2]3/2
b) R= [C2H4] [I2]3
c) R= [C2H4] [I2]2
d) R= [C2H4] [I2]
View Answer
Explanation: Fractional order reactions are reaction whose order is a fraction. This reaction is an example of fractional order reaction, where the order of the reaction is
The rate law for the reaction is known to be R= [C2H4] [I2]3/2.
10. The rate law for the reaction involved in inversion of cane sugar is R=k [C12H22O11] [H2O].
a) True
b) False
View Answer
Explanation: The reaction for the inversion of cane sugar is C12H22O11 + H2O → glucose + fructose.
In this reaction water is present in excess and belongs to a pseudo first order reaction, even though the molecularity is 2 the order of the reaction is 1 so the rate law R=k[C12H22O11].
Surface Chemistry
1. A finely divided substance is more effective as an adsorbent.
a) True
b) False
View Answer
Explanation: Adsorption is a surface phenomenon. It is dependent on the amount of the adsorbent exposed to the adsorbate. A finely divided substance provides a large surface area and hence, provides more sites where adsorption can take place.
2. What is the process called when the molecules of a substance are retained at the surface of a solid or a liquid?
a) Absorption
b) Adsorption
c) Sorption
d) Desorption
View Answer
Explanation: Adsorption is the process which involves the accumulation of the molecules of a substance in higher concentration on the surface of a solid or a liquid. For example, gasses are adsorbed on the surface of charcoal.
3. Which of the following forces is involved in physical adsorption?
a) Gravitational force
b) Magnetic force
c) Van der Waals force
d) Electromagnetic force
View Answer
Explanation: In physical adsorption, the molecules of the adsorbate stick to the surface of the adsorbent due to very weak forces which is known as Van der Waals force. Van der Waals force is similar to the forces that cause condensation of gas into liquid.
4. In physisorption, the adsorbent does not show specificity towards a particular gas.
a) True
b) False
View Answer
Explanation: In physisorption, there is no chemical bond between the adsorbent and adsorbate. They are held together by Van der Waals forces. Since Van der Waals forces are universal and almost same for all gases, the adsorbent does not show specificity to a particular gas.
5. Which of the following statements is true with respect to the extent of physisorption?
a) Increases with increase in temperature
b) Decreases with increase in surface area
c) Decreases with increase in the strength of Van der Waals forces
d) Decreases with increase in temperature
View Answer
Explanation: Physisorption is an exothermic process. According to Le-Chatelier’s principle, an exothermic reaction is favoured by a decrease in temperature. Therefore, the extent of physisorption decreases on increasing temperature.
a) Decrease in temperature
b) Increase in temperature
c) Decrease in pressure
d) Increase in surface area
View Answer
Explanation: Physisorption occurs due to Van der Waals forces. On increasing the temperature, the adsorbate can split into atoms and form chemical bonds with the adsorbent and hence, cause chemisorption.
7. Which of the following statements is incorrect with respect to physisorption?
a) It is reversible
b) It is spontaneous
c) ΔH < 0
d) ΔS > 0
View Answer
Explanation: Physisorption is reversible as the molecules of the adsorbate are held to the adsorbent by weak Van der Waals forces which can be broken easily. Physisorption is exothermic and so, ΔH is negative. Adsorption is a spontaneous process. In adsorption, the movement of the adsorbed molecule is restricted. As a result the entropy change (ΔS) is negative.
8. Which of the following statements is true with respect to the types of adsorption?
a) Chemisorption is stronger than physisorption
b) Physisorption is stronger than chemisorption
c) They are both equal
d) They cannot be compared
View Answer
Explanation: Chemisorption is stronger than physisorption. Chemisorption involves the forming of a chemical bond between the adsorbent and the adsorbate whereas in physisorption, the molecules are held together by weak Van der Waal’s forces. Therefore, chemisorption is stronger.
9. Which of the following is an example of sorption?
a) Sponge in water
b) Cotton dipped in ink
c) Water on silica gel
d) Oxygen on metal surface
View Answer
Explanation: Sorption refers to the process where adsorption and absorption occur at the same time. Cotton dipped in ink is one of the cases where both adsorption and absorption, that is, sorption occurs.
10. Which of the following statements is not true with respect to chemisorption?
a) Depends on nature of adsorbate and adsorbent
b) Has a large heat of adsorption
c) Forms a unimolecular layer
d) Occurs at low temperature
View Answer
Explanation: Chemisorption is a kind of adsorption that involves a chemical reaction between the adsorbent and adsorbate, resulting in the formation of a chemical bond between the two. Since a bond is to be formed, chemisorption is highly dependent on the reactants(adsorbate and adsorbent) and has a large heat of adsorption. Also, since it involves bond formation, it cannot be multi-layered. Chemisorption is favoured to occur at high temperature.
General Principles and Processes of Isolation of Elements
1. Which of the following is the chief ore of aluminium?
a) Kaolinite
b) Bauxite
c) Malachite
d) Cinnabar
View Answer
Explanation: Bauxite is the chief ore of aluminium. The composition of bauxite is Al2O3.2H2O, it’s a mixture of hydrated iron oxide and hydrated aluminium oxide. Kaolinite is another ore of aluminium but its less availability is less compare to bauxite and the extraction of aluminium from kaolinite is a hard process and costs more.
2. Which of the following is the finest iron ore?
a) Hematite
b) Magnetite
c) Siderite
d) Iron Pyrites
View Answer
Explanation: Magnetite is the finest iron ore with a very high content of iron up to 72 percent. It has a very good magnetic property and is valuable in electrical industry. Hematite is another very important iron ore but the iron content of hematite is slightly lower than magnetite.
3. What is the composition of Kaolinite?
a) Fe2O3
b) Al2O3.2H2O
c) [Al2(OH)4Si2O4]
d) CuFeS2
View Answer
Explanation: Kaolinite is a soft clay type material with the chemical composition [Al2(OH)4Si2O4]. It’s basically made up of hydrous aluminium silicates, they comprise the principle ingredients of kaolin (china clay). It is usually white in appearance and sometimes red due to iron oxide.
4. What is the composition of brass?
a) 49 percent copper and 51 percent zinc
b) 50 percent copper and 50 percent zinc
c) 37 percent copper and 63 percent zinc
d) 63 percent copper and 37 percent zinc
View Answer
Explanation: Brass is an alloy of copper and zinc, typically 63 percent copper and 37 percent zinc. Sometimes poor quality brass may contain a little lead. Brass is naturally corrosion resistant and has very low friction. It is used for construction of water pipes and fittings.
5. Which of the following is not a suitable ore for extracting iron?
a) Hematite
b) Magnetite
c) Siderite
d) Iron Pyrites
View Answer
Explanation: The composition of iron pyrite is FeS2. Iron pyrite is exothermic and can cause hazard in mines, it is more economical to extract iron from other ores such as magnetite and hematite. Pyrites are generally unstable and might turn into sulfurous minerals.
a) True
b) False
View Answer
Explanation: Malachite is a copper ore with composition CuCO3.Cu(OH)2. It contains around 58 percent copper and is bright green in color, it is a hydrous carbonate mineral and it’s a common but minor ore of copper.
7. What is the concentration of zinc in calamine?
a) 98 percent
b) 94 percent
c) 86 percent
d) 74 percent
View Answer
Explanation: The chemical composition of calamine is ZnCO3 with 98 percent concentration of zinc. It is available in abundance and can be artificially prepared in laboratories. It is used in medication to relieve pain and itching.
8. The composition of bronze is generally 82 percent copper and 18 percent tin.
a) True
b) False
View Answer
Explanation: Bronze is an alloy consisting mainly of copper and with other metals generally tin. The composition of bronze is 88 percent copper and 12 percent tin it may also contain small amount of aluminium, manganese, zinc and silicon.
9. Silver is extracted from which of the following ore?
a) Calamine
b) Cinnabar
c) Argentite
d) Malachite
View Answer
Explanation: Argentite also knows as silver glance is the only given silver ore in the above options with chemical composition Ag2S. Silver is extracted from silver glance by a simple process known as smelting or chemical leaching.
10. Which metal is extracted from Cinnabar?
a) Zinc
b) Copper
c) Iron
d) Mercury
View Answer
Explanation: Cinnabar also known as cinnabarite is a natural and the only important ore of mercury with chemical composition HgS. Cinnabar is a toxic ore because of the presence of high amount of mercury and cannot be handled directly.
p-Block Elements
1. Which of the following represents the general electronic configuration of an element belonging to the p-block of the periodic table?
a) (n-2)f0(n-1)d0ns2 np0 -6
b) (n-2)f0(n-1)d1 – 10 ns2 np1- 6
c) (n-2)f0(n-1)d0 ns2np1-6
d) (n-2)f1- 14(n-1)d1- 10ns2np1- 6
View Answer
Explanation: The general configuration representation of p-block elements is (n-2)f0(n-1)d0ns2np1-6. This is because the s-subshell is completely filled, whereas, the p-subshell contains at least 1 electron. Other options are ruled out since either or both d – and f – subshell are partially filled.
2. What happens to the size of atoms of elements of p-block as we move from left to right in the same period?
a) Size increases
b) Size decreases
c) Size does not change
d) Size increases then decreases
View Answer
Explanation: The size of the atoms of the elements decrease from left to right in the same period. Considering the row to be the same, the electrons are added to the same shell. However, the increase in atomic number reflects the increase in number of protons i.e. the positive charge. Hence, the overall effective nuclear charge increases. Consequently, the electron cloud is pulled even more closer to the nucleus of the atom. Therefore, the size decreases.
3. What is the maximum covalency of the nitrogen atom?
a) One
b) Two
c) Three
d) Four
View Answer
Explanation: Covalency of an atom refers to the number of electrons that atom can share to form chemical bonds. Usually it is the number of bonds formed by the atom. In case of nitrogen, its atom can share up to four electrons, one in the s-subshell and the other three in the p-subshell. In addition to this, absence of d-orbitals restricts its covalency to four only.
a) N atom can form multiple pπ – pπ bonds
b) Octet of N2 is complete unlike carbon
c) The N ≡ N is unreactive at room temperature
d) The N – N single bond is weaker and unstable
View Answer
Explanation: The N – N single bond is highly weak and unstable due to high magnitude of inter-electronic repulsions of non-bonding electrons which in turn is caused by the single bond’s small bond length. As a result the catenation tendency becomes weaker due to the mentioned factors leading to instability.
5. What is the primary product of Haber-Bosch process?
a) Ammonia
b) Nitric acid
c) Nitrous acid
d) Pyridine
View Answer
Explanation: The primary product of Haber-Bosch process is ammonia, NH3. In this process, N2(g) and H2(g) are reacted at a high temperature of 700 K and 200 atm pressure in presence of iron-bed catalysts. It is an exothermic process which takes place in accordance with Le Chatelier’s principle. Nitric acid is produced by Ostwald’s process. Nitrous acid is produced by reacting sodium nitrite with a mineral and pyridine by Chichibabin process.
6. Which gas is released when copper chips are subjected to concentrated nitric acid?
a) Nitrogen (I) oxide
b) Nitrogen (II) oxide
c) Nitrogen (III) oxide
d) Nitrogen (IV) oxide
View Answer
Explanation: Treating copper chips with concentrated nitric acid releases toxic brown gas, NO2, nitrogen (IV) oxide. It is a reddish-brown gas with pungent odor.
7. What shape is the HNO3 molecule in its gaseous state?
a) Bent
b) Linear
c) Planar
d) See Saw
View Answer
Explanation: In the gas state, the nitric acid molecule has a triangular planar shape with a steric number of 3 no lone pairs of electron. There are two major resonance forms of nitric acid.
8. Which of the following ions is the brown ring test useful for determining?
a) NO2–
b) NO2+
c) NO2
d) NO3–
View Answer
Explanation: The brown ring test is used to determine the presence of nitrate ions, NO3–. Dilute ferrous sulfate solution is added to solution containing nitrate ion. Following this, concentrated sulfuric acid is added along the sides of the test tube. A brown ring is formed at the junction concentrated sulfuric acid and solutions.
9. What catalyst is used for oxidation of ammonia to produce nitric acid?
a) Palladium hydride
b) Sodium amalgam
c) Platinum-Rhodium gauze
d) Vanadium (V) oxide
View Answer
Explanation: Ammonia is oxidized to nitrogen (II) oxide in the presence of Pt/Rh gauze catalyst at a temperature of 500 K and a pressure of 9 bars. The nitrous oxide is then converted to nitrogen dioxide which is further reacted with water to produce nitric acid. The NO formed is recycled.
10. What is the oxidation state of nitrogen in di-nitrogen trioxide?
a) +1
b) +2
c) +3
d) +4
View Answer
Explanation: Di-nitrogen trioxide is formulated as N2O3
The oxidation state of oxygen atom is fixed at -2 since it is the more electronegative atom in this case.
If oxidation state of nitrogen is assumed to be ‘x’, then:
2x + (3x -2) = 0
2x – 6 = 0
x = +3
The oxidation state of nitrogen is +3.
d and f Block Elements
1. Which metal is used in an aircraft turbine engine?
a) Iron
b) Thorium
c) Titanium
d) Neodymium
View Answer
Explanation: Titanium is one such material which plays a pivotal role in modern jet engine design. Its strength to weight ratio and resistance to extreme heat make it the ideal candidate for aerospace applications. Hence, it is used in aircraft turbine engines.
2. Mild steel is used in construction.
a) True
b) False
View Answer
Explanation: Plain Carbon Steel is the most common type of steel used in building construction, which is also known as mild steel. It is incalculably strong and durable, and ensures a sturdy built and used in various type of construction.
3. Which metal is used as an electroplated protective coating?
a) Plutonium
b) Chromium
c) Nickel
d) Iron
View Answer
Explanation: Chrome plating (less commonly chromium plating), often referred to simply as chrome, is a technique of electroplating a thin layer of chromium onto a metal object. The chromed layer can be decorative, provide corrosion resistance, ease cleaning procedures, or increase surface hardness.
a) Actinium
b) Nickel
c) Thorium
d) Tungsten
View Answer
Explanation: The melting point of Tungsten (W) is very high (3422°C). It has the highest melting point among all the metals. This property of Tungsten makes it excellent for use as filaments in light bulbs as it can resist high temperatures.
5. Silver bromide is used in photography.
a) True
b) False
View Answer
Explanation: Silver bromide (AgBr), a soft, pale-yellow, water-insoluble salt well known (along with other silver halides) for its unusual sensitivity to light. AgBr is widely used in photographic films and is believed by some to have been used for making the Shroud of Turin.
6. Which of the following metal does not form a coloured salt?
a) Thorium
b) Zinc
c) Bronze
d) Cobalt
View Answer
Explanation: Zinc has no unpaired electrons in its d orbital and has a stable fully filled d orbital. Hence, due to the absence of unpaired electrons in Zinc, it can show no specific colouration in its salts. All salts and solutions of Zinc are always white due to this fact.
7. Which of the following is used as a nuclear fuel?
a) Cobalt
b) Zinc
c) Iron
d) Uranium
View Answer
Explanation: Uranium (atomic no. 92, symbol-U) is used as nuclear fuel. Its salts are used in the glass industry (for imparting green colour), textile industry, ceramic industry and in medicines. Natural uranium has three major isotopes.
8. Which of the following has the highest density?
a) Os
b) Zn
c) Cr
d) Cd
View Answer
Explanation: Osmium is the densest naturally occurring element, with an experimentally measured (using x-ray crystallography) density of 22.59 g/cm3. Its atoms are packed together more tightly in the solid form than other metals.
9. Which of the following element has the highest melting point?
a) Co
b) Zn
c) Ni
d) Cr
View Answer
Explanation: Of all the 3d transition elements, chromium has the highest melting point. More the number of unpaired electrons in the d-block element, stronger is the metallic bond formation. Since chromium contains more number of unpaired electrons, it has the highest melting point.
10. What is the end product formed when KMnO4 reacts with HCl?
a) Brown fumes
b) Dark green gas
c) Greenish yellow gas
d) Dense white fumes
View Answer
Explanation: Potassium permanganate (KMnO4) reacts with hydrochloric acid(HCl) to form potassium chloride, manganese chloride, chlorine and water. Here, one of the products formed, chlorine, is a greenish yellow gas. It has a pungent smell and is toxic.
.jpeg)
.png)
0 Comments