Description : Diamond does not conduct electricity, because - (1) It's structure is very compact (2) It is of crystalline nature (3) There are only carbon atoms present in it (4) No free electrons are present in it
Last Answer : (4) No free electrons are present in it Explanation: Diamond has a giant molecular structure. Each carbon atom is covalently bonded to four other car-bon atoms. There are no ... conduct electricity. Except for most blue diamonds, which are semiconductors, diamonds are good electrical insulators.
Description : Diamond is harder than graphite because of – (1) difference in layers of atoms (2) tetrahedral structure of diamond (3) difference of crystalline structures (4) None of these
Last Answer : (1) difference in layers of atoms Explanation: Diamond is harder than graphite because diamond has a more complex structure. Diamond's structure is like many pentagons connected together, each pentagon ... together in some way. Graphite's structure is very loose, with its bonds forming layers.
Description : Diamond is harder than graphite because of : (1) difference in layers of atoms (2) tetrahedral structure of diamond (3) difference of crystalline structures (4) None of these
Last Answer : difference in layers of atoms
Description : (a) Show on a diagram the transfer of electrons between the atoms in the formation of MgO. Write symbols of cation and anion present in MgO. (b) Name the solvent in which ionic compounds are generally soluble. (c) Why are aqueous solutions of ionic compounds able to conduct electricity? -Chemistry
Last Answer : (b) Ionic compounds are soluble in water. (c) It is because aqueous solutions consist of ions which can move freely in them and carry current.
Description : (a) Show the formation of Na2O by the transfer of electrons between the combining atoms. (b) Why are ionic compounds usually hard? (c) How is it that ionic compounds in the solid state do not conduct electricity but they do so when in molten state? -Chemistry
Last Answer : (b) It is due to strong force of attraction between oppositely charged ions. (c) In solid state, ions are not free to move whereas in molten state ions are free to move, therefore, they conduct electricity in molten state.
Description : Pick out the correct statement. (A) Plastics are good conductors of heat and electricity (B) All the polymers are highly crystalline in nature (C) Polymers can be vaporised by heating to ... D) The liquid polymer becomes greasy, then waxy and finally solid on increasing the degree of polymerisation
Last Answer : (D) The liquid polymer becomes greasy, then waxy and finally solid on increasing the degree of polymerisation
Description : Metals are good conductors of electricity because (a) The contain free electrons (b) The atoms are lightly packed (c) They have high melting point (d) All of the above
Last Answer : Ans:(b)
Description : Metals are good conductors of electricity because - (1) they contain free electrons (2) the atoms are lightly packed (3) they have high melting point (4) All of the above
Last Answer : (1) they contain free electrons Explanation: Copper is used for electrical wiring because it is a good conductor of electricity. Metal particles are held together by strong metallic bonds, which is why they have high melting and boiling points.
Description : Metals are good conductors of electricity because – (1) they contain free electrons (2) the atoms are lightly packed (3) they have high melting point (4) All of the above
Description : In which of the following substances all carbon atoms are quaternary in nature ? (1) Graphite (2) Diamond (3) Teflon (4) Napthalene
Last Answer : Diamond
Description : Diamond has each of the following properties except: w) extreme hardness x) ability to conduct electricity y) high melting point z) tendency to burn in air
Last Answer : ANSWER: X -- ABILITY TO CONDUCT ELECTRICITY
Description : Diamond is the form of carbon that is (a) Crystalline (b) Amorphous (c) Chemical (d) Alkaline
Last Answer : Ans:(a)
Description : Diamond is the form of carbon that is - (1) Crystalline (2) Amorphous (3) Chemical (4) Alkaline
Last Answer : (1) Crystalline Explanation: Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic.
Description : Why is diamond hard whereas graphite soft even through both are crystalline forms of carbon?
Last Answer : The reason for difference is because of arrangement of carbon atoms.
Description : Solids may be considered to be either crystalline noncrystalline. The basic difference between them is that a crystal, in contrast to a noncrystal: w) has a sharp melting point x) has an irregular array of atoms y) exhibits double refraction z) has a completely regular atomic or molecular structure
Last Answer : ANSWER: Z -- HAS A COMPLETELY REGULAR ATOMIC OR MOLECULAR STRUCTURE
Description : Elements that do not conduct electricity and heat which tends to accept electrons?
Last Answer : Non-Metals
Description : Elements that conduct electricity and heat which tends to lose electrons are called?
Last Answer : Metals
Description : Superconductors are those elements – (1) Whose conductivity is intermediate between metals and insulators (2) Whose resistance falls almost to zero at very low temperature (3) Which conduct electricity only at super-high temperature (4) Which conduct electricity only, at super-high temperatures
Last Answer : (2) Whose resistance falls almost to zero at very low temperature Explanation: Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in ... lines from the interior of the superconductor as it transitions into the superconducting state.
Description : Superconductors are those elements (1) Whose conductivity is intermediate between metals and insulators (2) Whose resistance falls almost to zero at very low temperatures (3) which turn into insulators at very low temperatures (4) which conduct electricity only at super-high temperatures
Last Answer : Whose resistance falls almost to zero at very low temperatures
Description : The noble gases have low boiling points because: w) their ionization potentials are very low x) only weak Van der Waals forces hold the atoms together y) they are produced by the fractional distillation of liquid air z) they have eight electrons in the outer shell
Last Answer : ANSWER: X -- ONLY WEAK VAN DER WAALS FORCES HOLD THE ATOMS TOGETHER
Description : Decarburisation of steel (A) Is the removal of carbon from iron carbide (Fe3C) (B) Affects its crystalline structure (C) Is favoured by CO2 (D) All (A), (B) and (C)
Last Answer : (D) All (A), (B) and (C)
Description : Benzene undergoes substitution reaction more easily than addition reaction because (a) it has a cyclic structure (b) it has three double bonds (c) it has six hydrogen atoms (d) there is delocalization of electrons
Last Answer : there is delocalization of electrons
Description : All of the following substances are crystalline except-------? A. Ice B. Diamond C. Sucrose D. Plastic (Answer)
Last Answer : D. Plastic (Answer)
Description : Which of the following is NOT a physical property of crystalline boron? w) brown color x) diamond hardness y) brittleness z) high electrical resistance
Last Answer : ANSWER: W -- BROWN COLOR (Crystalline boron is transparent.)
Description : Write the name and structure of a saturated compound in which the carbon atoms are shaped in a ring. Also write the number of bonds present in that compound? -SST 10th
Last Answer : It’s cyclo alkane, it can be any cyclo alkane like cyclo pentane or cyclo hexane.
Description : What is not True for DNA in prokaryotes a) present in the form of a compact structure called nucleoid b) the coils are maintained by non-histone basic proteins c) found in cytoplasm in a supercoiled condition d) packaged as nucleosomes along with histones
Last Answer : b) the coils are maintained by non-histone basic proteins
Description : .Mad cow disease in cattle is caused by an organism which has (a) inert crystalline structure (b) abnormally folded protein (c) free RNA without protein coat (d) free DNA without protein coat.
Last Answer : (b) abnormally folded protein
Description : As which one of the following, does carbon occur in its purest form in nature? (1) Carbon black (2) Graphite (3) Diamond (4) Coal
Last Answer : (3) Diamond Explanation: The purest form of carbon is neither diamond nor graphene or graphite . It is 'Fullerene' , the purest form of carbon.
Description : Metals are good conductors of electricity because they have: (a) Large number of bounded electrons (b) Small number of electrons (c) Large number of free electrons (d) Small number of free electrons
Last Answer : (c) Large number of free electrons
Description : Which of the following statements about benzene is correct? (a) All of the carbon atoms are sp3 hybridized. (b) It has no delocalized electrons. (c) The carbon-carbon bond length is longer than that of ethane. (d) It is a planar molecule.
Last Answer : It is a planar molecule.
Description : Carbon occurs in nature in the purest form as (a) Diamond (b) Graphite (c) Carbon black (d) Coal
Description : Carbon occurs in nature in the purest form as - (1) Diamond (2) Graphite (3) Carbon black (4) Coal
Last Answer : (1) Diamond Explanation: There are three forms of pure carbon: Graphite, Coal and Diamond. All three are made up of elemental carbon, caol is the least pure when found in nature. Diamond is the purest form of Carbon.
Description : A solid is which atoms are in a regular order is called a) Crystalline solid b) Amorphous solid c) Polymeric solid d) Glassy solid
Last Answer : a) Crystalline solid
Description : PVC stands for (A) Plastic very compact (B) Polythene vinyl chloride (C) Polythene vinyl carbon (D) Polythene vanadium carbide
Last Answer : Answer: Option B
Description : The lustre of the metals is because of (1) high density, due to closed packing of atoms (2) high polish (3) reflection of light due to the presence of free electrons (4) absorption of light due to the presence of cavities
Last Answer : reflection of light due to the presence of free electrons
Description : The Himalayan region is poor in mineral resources because (a) it is made up of crystalline rocks (b) displacement of rock strata has disturbed the arrangement of rocks and made it ... minerals (d) the terrain makes exploitation of minerals difficult and very costly due to transport difficulties
Last Answer : Ans: (b)
Description : The Himalayan region is poor in mineral resources because: [IAS 2004] (a) it is made of crystalline rocks (b) the displacement of rock strata has disturbed the arrangement of rock and ... minerals (d) the terrain makes exploitation of minerals difficult and very costly due to transport difficulties
Description : Which of the following is not characteristic of resonance? (a) The canonical structures have the constituent atoms in the same relative positions (b) They have nearly the same energy (c) ... of unpaired electrons (d) The actual structure can be represented on paper using the conventional symbols
Last Answer : Ans:(d)
Description : Atoms of U-238 and U-235 differ in structure by three (A) Electrons and three protons (B) Protons (C) Neutrons (D) Electrons
Last Answer : (C) Neutrons
Description : How does a compact fluorescent lamp consume less electricity than conventional fluorescent lamps and bulbs?
Last Answer : Fluorescent lamps are based on the phenomenon of gas discharge between two electrodes at the ends of a glass tube. Generally these tubes contain a little mercury in the low-pressure vapour phase. When ... poor efficiency. The three types of lamps may have a typical efficiency ratio of 8:6:3.
Description : Which of the following is false? a) electricity is high-grade energy b) high grade forms of energy are highly ordered and compact c) low grade energy is better used for applications like melting of metals rather than heating water for bath
Last Answer : c) low grade energy is better used for applications like melting of metals rather than heating water for bath
Description : A homeowner replaces a 65 watt incandescent bulb with a 15 watt compact fluorescent lamp. The light is on 2000 hours a year. If electricity cost 10 cents a kilowatt-hour, how much money is saved on the electric bill in one year? w) $50.00 x) $10.00 y) $5.00 z) $1.00
Last Answer : ANSWER: X -- $10.00
Description : Most of the fibre forming polymers are crystalline in nature, one of the exceptions being __________ which is amorphous in nature. (A) Nylon (B) Polyacrylonitrile (C) Polypropylene (D) Polyester
Last Answer : (B) Polyacrylonitrile
Description : While the thermosetting polymers are amorphous in nature, the thermoplastic polymers are either amorphous or crystalline. The crystalline polymers are characterised by the (A) Low impact strength (B) High flexibility (C) Better finish and surface appearance (D) High plastic deformation
Last Answer : A) Low impact strength
Description : Super conductors are those substances, which (A) Offer no resistance to current flow (B) Conduct electricity at low temperature (C) Offer high resistance to current flow (D) Conduct electricity at high temperature
Last Answer : (A) Offer no resistance to current flow
Description : Which of the following is not a characteristic of organic compounds? (a) They usually have low melting points. (b) They usually are only slightly soluble or insoluble in water. (c) If water ... they seldom conduct an electric current. (d) Bonds which bind the atoms together are nearly always ionic.
Last Answer : Bonds which bind the atoms together are nearly always ionic.
Description : Fibres are of crystalline structure. Why ?
Last Answer : Ans. Fibres have strong intermolecular forces of attraction which leads to close packing of their chains and impart crystalline structure.
Description : The two elements required to form substitutional solid solution should not have (A) Same crystalline structure (B) Same valency (C) Widely differing electronegativity (D) Same atomic sizes
Last Answer : C) Widely differing electronegativity