Chemistry GK Questions Quiz-37

Chemistry GK Questions Quiz-37

Chemistry Multiple Choice Questions (MCQs) Quiz for State and UPSC Civil Services Examinations. Objective Questions on Chemistry for competitive examinations.

    721. Number of neutrons in an atom of hydrogen is

    (1) One 
    (2) Zero
    (3) Two 
    (4) Three
    Answer:
    721. (2) Neutrons are the particles in an atom that have a neutral charge. So, if an atom has equal numbers of electrons and protons, the charges cancel each other out and the atom has a neutral charge. Hydrogen (H) has 1 proton and 1 electron; it does not have any neutron in its nucleus.

    722. The heat value of combustion of Gasoline is

    (1) 12600 kJ/kg
    (2) 14600 kJ/kg
    (3) 39400 kJ/kg
    (4) 47000 kJ/kg
    Answer:
    722. (4) The calorific value of Gasoline is 47,300 kJ/kg. The calorific value of a fuel is the quantity of heat produced by its combustion - at constant pressure and under “normal” conditions (i.e. to 0oC and under a pressure of 1,013 mbar).

    723. Who developed the model of atomic structure ?

    (1) Bohr and Rutherford
    (2) Volta
    (3) Alfred Nobel
    (4) Faraday
    Answer:
    723. (1) In 1911 Ernest Rutherford used experimental evidence to show that an atom must contain a central nucleus. Niels Bohr further developed Rutherford’s nuclear atom model. He used experimental evidence to support the idea that electrons occupy particular orbits or shells around the nucleus of an atom.

    724. Sodium Carbonate is commonly known as

    (1) Baking Soda
    (2) Washing Soda
    (3) Caustic Soda
    (4) Caustic Potash
    Answer:
    724. (2)Sodium carbonate (Na2CO3) is also known as washing soda, soda ash and soda crystals. It is a salt of carbonic acid, a chemical that produces a wide range of salts collectively known as carbonates. It can be used to remove stubborn stains from laundry.

    725. When a bond is formed between two atoms, the energy of the system will

    (1) increase
    (2) decrease
    (3) remain the same
    (4) may increase or decrease
    Answer:
    725. (3) The fundamental reason for the bonding of atoms is that they lose their stored potential energy by forming bonds. This is the only reason for chemical combination. So, when a bond is formed between two atoms, stored potential energy is always released to the surroundings. However, according to the Law of Conservation of Energy, a bond cannot form unless this bond energy is transferred from the interacting atoms to the rest of the system. So overall the energy of the system remains the same.

    726. If the equilibrium constants for the systems H2 + I2 ®¬ 2HI and2HI ®¬ H2 + I2 are K1 and K2 respectively, the relationship between K1 and K2 is :

    (1) K1 = K2 
    (2) K1 = 2K2
    (3) K1 =K22 
    (4) K1 =1 K2
    Answer:
    726. (4) As per the Law of Mass Action, if Kf is the equilibrium constant for the equation A + B C + D, then 1/Kf is the equilibrium constant for the reverse equation, C + D A + B. So, as per the question K1 is the equilibrium constant for H2 + I2 2 HI, then 1/K1 is equilibrium constant for the reverse equation 2 HI H2 + I2

    727. Concentration of a material which is lethal to 50% animal is called

    (1) LD50 
    (2) LC50
    (3) NOAEL 
    (4) ADI
    Answer:
    727. (1) LD50 (Lethal Dose 50) is the amount of a solid or liquid material that it takes to kill 50% of test animals (for example, mice or rats) in one dose. LD50 is one way to measure the short-term poisoning potential (acute toxicity) of a material. LC50 is the concentration of a material in air that will kill 50% of the test subjects when administered as a single exposure.

    728. Muddy water is treated with alum in purification process, itis termed as :

    (1) emulsification 
    (2)absorption
    (3) adsorption 
    (4) coagulation
    Answer:
    728. (4) Natural and wastewater contain small particulates that are suspended in water forming a colloid. These particles carry the same charges, and repulsion prevents them from combining into larger particulates to settle. Historically, dirty water is cleaned by treating with alum, Al2(SO4)3.12 H2O, and lime, Ca(OH)2. The phenomenon is known as coagulation:Al2(SO4)3.12 H2O Al(aq)3+ + 3SO4(aq)2- + 12H2OSO4(aq)2- + H2O HSO4(aq)- + OH- (causing pH change)Ca(OH)2 Ca(aq)2+ + 2 OH- (causing pH change) The slightly basic water causes Al(OH)3, Fe(OH)3 and Fe(OH)2 to precipitate, bringing the small particulates with them and the water becomes clear.

    729. Brass contains

    (1) Copper and Zinc
    (2) Copper and Tin
    (3) Copper and Silver
    (4) Copper and Nickel
    Answer:
    729. (1)Brass is an alloy made of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties. By comparison, bronze is principally an alloy of copper and tin.

    730. Which is the purest commercial form of iron ?

    (1) Pig iron
    (2) Steel
    (3) Stainless steel
    (4) Wrought iron
    Answer:
    730. (4)Wrought iron or malleable iron is the purest form of commercial iron as it contains the lowest percentage of carbon (0.12-0.25%) and impurities of S, P, Mn and Si in minute amount (about 0.3%). It is made by melting cast iron with scrap iron in a reverberatory furnace lined with Fe2O3 which oxidizes C, Si, P, etc, most of which are then removed by rolling.

    731. In galvanization, iron is coated with

    (1) Copper 
    (2) Zinc
    (3) Tin 
    (4) Nickel
    Answer:
    731. (2)Galvanization is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanization, in which parts are submerged in a bath of molten zinc.

    732. Which one of the following is also know as solution ?

    (1) A compound
    (2) A homogeneous mixture
    (3) A heterogeneous mixture
    (4) A suspension
    Answer:
    732. (2)In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. The solution more or less takes on the characteristics of the solvent including its phase.

    733. A solution is

    (1) a homogeneous mixture of two or more substances
    (2) a solid dissolved in a liquid
    (3) a solid dissolved i water
    (4) a mixture of two liquids
    Answer:
    733. (1) A homogeneous mixture of two or more substances uniformly dispersed throughout a single phase is called solution. In such a mixture, a solute is a substance dissolved in another substance, known as a solvent. The solution more or less takes on the characteristics of the solvent including its phase, and the solvent is commonly the major fraction of the mixture.

    734. The first organic compound synthesised in the laboratory was

    (1) Urea 
    (2) Uric acid
    (3) Lactic acid 
    (4) Glucose
    Answer:
    734. (1) In 1828, German chemist Friedrish Wohler synthesized first organic compound, urea in the laboratory by heating ammonium cyanate (an inorganic compound). NH4CNO (Ammonium Cyanate) ® NH2CONH2 (Urea) Soon, Kolbe, in 1845, synthesized Acetic acid in laboratory from Carbon, Hydrogen and Oxygen.

    735. The buffer action of blood is due to the presence of

    (1) HCI and NaCI
    (2) CI– and CO32-
    (3) CI– and HCO3-
    (4) HCO3- and H2CO3
    Answer:
    735. (4) The most important buffer for maintaining acidbase balance in the blood is the carbonic-acid-bicarbonate buffer. Three different buffer systems exist in blood, the bicarbonate buffer and the phosphate buffer are composed of "simple" chemicals. In addition the carbonyl groups (-COOH) and the amide group (-NH2) present on proteins allow some of these to act as buffers.
    H2CO3 + H2O « HCO3- +H3O+H PO H O HPO H O 2 4 2 - + « 24- + 3 +

    736. Which one of the following contains maximum percentage of carbon ?

    (1) Cast iron
    (2) Stainless steel
    (3) Wrought iron
    (4) High speed steel
    Answer:
    736. (1) Cast Iron is a hard, brittle, nonmalleable iron-carbon alloy, cast into shape, containing 2 to 4.5 percent carbon. Steels contain less than 2% and usually less than 1% carbon, while all cast irons contain more than 2% carbon. Most steel contains less than 0.35 percent carbon. Wrought iron is an iron alloy with very low carbon (0.04 to 0.08%) content.

    737. Which of the following appeared to be with a significant potential for accumulation through food chains ?

    (1) DDT 
    (2) Parathion
    (3) Lindane 
    (4) Carbary
    Answer:
    737. (1) Mercury and DDT are two persistent toxic materials that accumulate in the food chain and damage the organisms in it. DDT is an insecticide that can pass up the food chain from insects to small birds, and then from the small birds to birds of prey. It is now banned because of this.

    738. Which one of the following elements is an example of noble gas ?

    (1) Nitrogen 
    (2) Hydrogen
    (3) Chlorine 
    (4) Helium
    Answer:
    738. (4) Noble gas refers to any of the seven chemical elements that make up Group VIIIa of the periodic table. The elements are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn), and element 118 (temporarily named ununoctium [Uuo]).

    739. Which of the following elements does not exhibit natural radioactivity ?

    (1) Uranium 
    (2) Thorium
    (3) Aluminium 
    (4) Polonium
    Answer:
    739. (3) Uranium, Thorium and Polonium are radioactive elements which do not have stable naturally occurring isotope. Aluminium is a silvery white, soft, ductile metal. It is the third most abundant element (after oxygen and silicon), and the most abundant metal in the Earth’s crust.

    740. The most abundant element is

    (1) Calcium 
    (2) Silicon
    (3) Oxygen 
    (4) Nitrogen
    Answer:
    740. (3) On earth, oxygen is the most common element, making up about 47% of the earth’s mass. Silicon is second, making up 28%, followed by aluminum (8%), iron (5%), magnesium (2%), calcium (4%), sodium (3%), and potassium (3%). All of the remaining elements together make up less than 1% of the earth’s mass.


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