Chemical Engineering Basics

141. Between 230 and 370°C, blue brittleness is caused in mild steel because of the

1. Immobility of dislocation
2. Strain-ageing
3. Increase in Young's modulus
4. Strain hardening

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142. Biological shield in a nuclear reactor is generally provided to protect against the

1. α-rays
2. β-rays
3. Gamma rays & neutrons
4. Electrons

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143. Blast furnace slag is mainly molten

1. Sand
2. Magnesium silicate
3. Calcium silicate
4. Iron pyrite

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144. Blasting of tri-nitro-toluene (TNT) is done by mixing it with ammonium

1. Nitrate
2. Sulphate
3. Carbonate
4. Chloride

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145. Blow off cock is provided in steam boiler to

1. Guard the boiler in case of abnormal rise in steam pressure
2. Drain out water and sludge during its repair
3. Regulate the supply of water in boiler
4. Put out the fire in the furnace when the water level in the boiler falls to unsafe limit

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146. Boiler draught of 10 mm water column is equivalent to

1. 1 kgf/m²
2. 10 kgf/m²
3. 10 kgf/mm²
4. 1 kgf/mm²

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147. Boiler tube size is specified by its thickness and __________ diameter.

1. Outside
2. Inside
3. Mean
4. None of these

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148. Boiling point of water gets lowered at high altitudes (e.g., hills), because

1. Temperature is low
2. Atmospheric pressure is low
3. Atmospheric pressure is high
4. None of these

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149. Brass parts with high residual tensile stress at the surface are susceptible to season crackin (i.e. spontaneous cracking occuring on exposure to atmospheric corrosion), if its zinc percentage is more than

1. 5
2. 10
3. 20
4. 35

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150. Brazing filler metal used for joining steel plates

1. Melts below the melting points of base metals
2. Melts below 300°C
3. Is copper phosphorous alloy
4. Is copper

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