Stoichiometry General Knowledge Multiple Choice Questions(MCQs) with Answers

61 An insulating refractory brick should have high porosity and low thermal conductivity. Which of the following is not used for inducing porosity in the insulating refractory bricks during its manufacture ?

A Cork

B Saw dust

C Sand

D Chemically prepared foam

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Answer: Sand

62 Test piece for determination of RUL of a refractory is heated in a/an__________________?

A Oxidising atmosphere

B Reducing atmosphere

C Electric furnace

D Neutral atmosphere

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Answer: Electric furnace

63 With increase in the alumina content, the refractoriness of high alumina refractories_________________?

A Increases

B Decreases

C Remain same

D May increase or decrease

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Answer: Increases

64 Thermal diffusivity of a refractory brick is high, when its ______________ is high?

A Density

B Specific heat

C Thermal conductivity

D None of these

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Answer: Thermal conductivity

65 Fusion point of a basic refractory material is________________?

A Reduced by the addition of acid oxides

B Increased by the addition of acid oxides

C Not affected by the addition of acid oxides

D Always less than 1000°C

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Answer: Reduced by the addition of acid oxides

66 Fireclay bricks are used in the______________?

A Coke ovens regenerator

B Outer lining of L.D. converter

C Hearth bottom of blast furnace

D Coke oven walls

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Answer: Coke ovens regenerator

67 High porosity refractory bricks have________________?

A Poor resistance to the penetration of molten slag, metal & flue gases

B Poor heat conductivity & low strength

C Better thermal spalling resistance

D All A., B. and C

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Answer: All A., B. and C

68 Fireclay bricks are not used in the________________?

A Beehive coke oven

B By-product coke oven walls

C Combustion chamber of B.F. stoves

D Coke oven regenerators

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Answer: By-product coke oven walls

69 Hot metal runner in blast furnace are lined with ______________ bricks?

A Silica

B Carborundum

C Fireclay

D Magnesite

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Answer: Fireclay

70 Presence of MgO in alumino-silicate refractories ______________ its refractoriness ?

A Increases

B Lowers

C Does not affect

D Either A. or B.; depends on its quantity

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Answer: Lowers

71 Chemically, mullite refractories is________________?

A 3Al2O3.2SiO2

B Al2O3

C ZrSO4

D ThO2

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Answer: 3Al2O3.2SiO2

72 Panel test determines the ______________ of refractories?

A Fusion point

B Spalling resistance

C Slag penetration resistance

D Refractoriness under load (RUL)

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Answer: Spalling resistance

73 Maximum alumina content in high alumina refractory can be as high as ____________ percent?

A 30

B 87

C 97

D 90

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Answer: 90

74 Water content in ground refractory material to be shaped into bricks by hand moulding is about _____________ percent?

A 5

B 20

C 40

D 55

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Answer: 20

75 Beryllia (which is used in making crucibles for melting uranium & thorium) is superior to alumina in all respects for high temperature (> 1900°C ) use, except______________?

A Cost

B Electrical conductivity

C Thermal conductivity

D Fusion point

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Answer: Cost

76 Refractory bricks with lower permeability is produced by using _________________?

A Higher firing temperature

B Higher moulding pressure

C Finer grog size

D All A., B. and C

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Answer: All A., B. and C

77 Refractories subjected to alternate cycles of heating & cooling are liable to loose their resistance to__________________?

A Thermal spalling

B Slag attack

C Fusion under load

D CO attack

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Answer: Thermal spalling

78 Addition of zircon to silica refractory brick improves its_________________?

A Crushing strength

B Resistance to slag attack

C Both A. and B.

D Neither A. nor B.

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Answer: Resistance to slag attack

79 Pick out the wrong statement?

A Atomic heat capacities of the crystalline solid elements are nearly constant and equal to 6.2 kcal/kg-atom according to the law of Petit and Dulong

B Atomic heat capacities of all solid elements decrease greatly with decrease in temperature, approaching a value of zero at absolute zero temperature, when in the crystalline state

C Generally, the heat capacities of compounds are lower in the liquid than in the solid state

D The heat capacity of a heterogeneous mixture is an additive property, but when solutions are formed, this additive property may no longer exist

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