Chemistry GK Questions Quiz-39

Chemistry GK Questions Quiz-39

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

    761. Ultra purification of a metal is done by :

    (1) slugging 
    (2) zone melting
    (3) smelting 
    (4) leaching
    761. (2) When metals are required in a ultra pure state, the zone refining method is used. The principle-employed states that the impurities, which lower the melting point of a metal remain preferentially dissolved in the liquid phase and purer metal will emerge in the solid phase.

    762. The soft silvery metalic element which ionizes easily when heated or exposed to light and is present in atomic clocks is :

    (1) Cerium 
    (2) Cesium
    (3) Calcium 
    (4) Califonrium
    762. (2) In 1967, based on Einstein defining the speed of light as the most constant dimension in the universe, the International System of Units isolated two specific wave counts from an emission spectrum of caesium-133 to co-define the second and the meter. Since then, caesium has been widely used in highly accurate atomic clocks. Among alkali metals, cesium has lowest ionization energy and hence it can show photoelectric effect to the maximum extent.

    763. Catalytic converters are generally made from :

    (1) Alkaline metals
    (2) Hydrogen
    (3) Transition metals
    (4) Carbon
    763. (3) Transition metals are used directly as catalysts in the anti–pollution catalytic converters in car exhausts. For example, expensive transition metals such as Platinum and rhodium are used in the catalytic converters in car exhausts to reduce the emission of carbon monoxide and nitrogen monoxide, which are converted to the non–polluting gases nitrogen and carbon dioxide.
    2NO (g) + 2CO(g) Þ N2 (g) + 2CO2 (g)

    764. The green colour seen in firework displays is due to the chloride salt of :

    (1) Sodium 
    (2) Strontium
    (3) Barium 
    (4) Calcium
    764. (3) The red, orange, yellow, green, blue and purple colors exploding in the night sky during a pyrotechnic festival are created by the use of metal salts. Barium chloride provides green colour to firework displays. Metal salts that are commonly used in firework displays include: strontium carbonate (red), calcium chloride (orange), sodium nitrate (yellow), barium chloride (green fireworks) and copper chloride (blue fireworks).

    765. The radiation that can penetrate deepest in our body

    (1) UV-radiation
    (2) Alpha-particles
    (3) b-particles
    (4) Gamma-particles
    765. (4) The ability of radioactivity to pass through materials is called its penetrating ability. Penetrating ability depends on the size of the radioactive particle. Alpha particles are the biggest, beta particles are very much smaller and gamma rays have no mass. Ultraviolet rays have less energetic photons compared to gamma rays and x-rays and a lower penetration power. Gamma rays are the most penetrating of the radiations.

    766. Which one of the following does not contain silver ?

    (1) Horn silver
    (2) Ruby silver
    (3) German silver
    (4) Lunar caustic
    766. (3) German Silver (also known as New Silver, Nickel Brass, etc) is a copper alloy with nickel and often zinc. The usual formulation is 60% copper, 20% nickel and 20% zinc. It is named for its silvery appearance, but it contains no elemental silver unless plated.

    767. An important green-house gas other than methane being produced from the agricultural fields is

    (1) Nitrous oxide
    (2) Ammonia
    (3) Sulphur dioxide
    (4) Arsine
    767. (1) Nitrous oxide (N2O) and methane (CH4) are the two major greenhouse gasses (GHG) emitted by agricultural activities. N2O accounts for around 8% of the warming impact of current human GHG emissions. Agricultural activities that directly increase N2O emissions are: fertilization, application of manure or other organic materials, retention of crop residues, production of nitrogen-fixing crops and forages, and cultivation of soils with high organic matter content. Irrigation, drainage, tillage practices and fallowing of land also increase N2O emission.

    768. Acid rain is caused due to pollution of atmosphere by

    (1) oxides of carbon and nitrogen
    (2) oxides of nitrogen and sulphur
    (3) oxides of nitrogen and phosphorus
    (4) None of these
    768. (2) Acid rain is caused by emissions of Sulfur Dioxide (SO2) and Nitrogen Oxide (NOx), which react with the water molecules in the atmosphere to produce acids. Emissions of SO2 and NOx result from fossil fuel combustion. The chemicals in acid rain can cause paint to peel, corrosion of steel structures such as bridges, and erosion of stone statues.

    769. Which of the following chemicals is responsible for depletion of ozone layer in the atmosphere?

    (1) Chlorofluorocarbons
    (2) Nitrous oxide
    (3) Sulphur dioxide
    (4) Carbon dioxide
    769. (1) Chlorofluorocarbon contributes to ozone depletion in the upper atmosphere. It is an organic compound that contains only carbon, chlorine, and fluorine, produced as a volatile derivative of methane, ethane, and propane. Its manufacture has been phased out under the Montreal Protocol.

    770. Chemical composition of heavy water is :

    (1) H2O2 
    (2) H2O
    (3) HDO 
    (4) D2O
    770. (4) The chemical composition of Heavy water (deuterium oxide) is 2H2O or D2O. It is a form of water that contains a larger than normal amount of the hydrogen isotope deuterium (2H or D, also known as heavy hydrogen), rather than the common hydrogen-1 isotope (1H or H, also called protium) that makes up most of the hydrogen in regular water.

    771. Oxide of sulphur present in the atmosphere are washed down by rains to cause :

    (1) Depletion of fossil fuel reserves
    (2) Eutrophication in lakes
    (3) Lowering of pH of soil
    (4) Industrial smog formation
    771. (1) The oxide of Sulphur (Sulphur Dioxide) is washed down on earth as acid rain. It makes the soil acidic by lowering its pH; this affects plants and animals adversely. Acid rain contains H+, SO42- ions which when added to the soil leaches the nutrients from the soil. Acid rain renders the river or even ocean water acidic, thereby affecting marine animals adversely. Changes in pH of fresh water affect the reproduction and survival or many species or fish.

    772. The acid which fails to liberate carbon dioxide from sodium bicarbonate is :

    (1) Acetic acid
    (2) Formic acid
    (3) Carbonic acid
    (4) Sulphuric acid
    772. (4) Sodium bicarbonate and organic acid (Formic acid, Acetic acid, Carbonic acid, etc) react vigorously to liberate carbon dioxide. For example, Sodium bicarbonate (NaHCO3) when treated with acetic acid reacts vigorously to liberate carbon dioxide. 
    NaHCO3 + CH3COOH ® CH3COONa + H2O + CO2

    773. Which one of the following is not coal variety?

    (1) Lignite 
    (2) Bituminous
    (3) Dolomite 
    (4) Peat
    773. (3) Dolomite is a common rock-forming mineral. It is a calcium magnesium carbonate with a chemical composition of CaMg(CO3)2. It is the primary component of the sedimentary rock known as dolostone and the metamorphic rock known as dolomitic marble. Dolomite is used in the Pidgeon process for the production of magnesium.

    774. Dry ice is the solid form of :

    (1) Air
    (2) Carbon di–oxide
    (3) Nitrogen 
    (4) Water
    774. (2) Dry ice, sometimes referred to as “cardice,” is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue. It is useful for preserving frozen foods, ice cream, etc., where mechanical cooling is unavailable.

    775. The common name of sodium bicarbonate is

    (1) Soda ash 
    (2) Baking soda
    (3) Soda lime 
    (4) Baking powder
    775. (2) Sodium bicarbonate (NaHCO3) is also known as baking soda, bread soda, cooking soda, and bicarbonate of soda. It is primarily used in cooking (baking), as a leavening agent. It reacts with acidic components in batters, releasing carbon dioxide, which causes expansion of the batter and forms the characteristic texture and grain in pancakes, cakes, quick breads, etc.

    776. If there is one million Mg2+ ions in MgCl2, how many chloride ions are there?

    (1) Two million 
    (2) One million
    (3) Half a million 
    (4) Ten million
    776. (1) Using formula of Stoichiometry, 1mol MgCl2 : 1mol Mg2+: 2mol Cl-. There are two moles of chloride ions for every one mole of MgCl2. So if there is one million Mg2+ ions in MgCl2, there will be two million chloride ions in it.

    777. The gas that causes suffocation and death when coal or coke is burnt in a closed room is

    (1) Methane
    (2) Ethane
    (3) Carbon monoxide
    (4) Carbon di–oxide
    777. (3) Exhaust fumes of motor cars, gases produced from coal fire in a closed room and coal gas, all contain carbon monoxide, which is the cause of their poisonous nature. When carbon monoxide is inhaled, it prevents the oxygen from combining with hemoglobin and instead combines itself with hemoglobin to form carboxyhaemoglobin, which is stable compound. This causes oxygen starvation in the body tissues and eventually causes death by suffocation.

    778. Air is said to be saturated when :

    (1) it contains maximum content of water vapour
    (2) its pressure is minimum
    (3) its thickness is maximum
    (4) it blows over the barren land
    778. (1) When a volume of air at a given temperature holds the maximum amount of water vapour, the air is said to be saturated. Air is said to be saturated at 100 percent relative humidity when it contains the maximum amount of moisture possible at that specific temperature. When relative humidity reaches 100 percent or is saturated, moisture will condense, meaning the water vapor changes to liquid vapor.

    779. Atoms having the same number of protons but different number of neutrons are called :

    (1) Isotopes 
    (2) Cations
    (3) Higgs-boson 
    (4) Anions
    779. (1) Atoms that have the same number of protons but different numbers of neutrons are called isotopes. For example, carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13 and 14 respectively. The atomic number of carbon is 6, which means that every carbon atom has 6 protons, so that the neutron numbers of these isotopes are 6, 7 and 8 respectively.

    780. Soap helps in better cleaning of clothes because

    (1) Soap acts like catalyst
    (2) It reduces the surface tension of solution
    (3) It gives strength to solution
    (4) It absorbs the dirt
    780. (2) Soaps are effective cleaners because they can dissolve and the oil and grease that holds dirt in place. They reduce the surface tension of the solution and enable it to wet things more uniformly. The surfactants in detergents improve water’s ability to wet things, spread over surfaces, and seep into dirty
    clothes fibers. The surfactant molecules help water to get a hold of grease, break it up, and wash it away.

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