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.Management Sciences
Category: Gypsum Products
Placing cast under tap water is to be avoided as______________?
A. H2O interferes with hygroscopic expansion
B. H2O inhibits polymerization of dental resin
C. H2O interferes with Crystallization of dihydrate
D. Gypsum is slightly soluble in water and the surface of the cast will be eroded
Gillmore needle is used for_______________?
A. Testing the strength of plaster of paris
B. Evaluating the setting time of plaster of pris
C. Testing the metal hardness
D. Testing the purity of noble metals
Setting of POP is result of______________?
A. Difference in solubility of CaSo4 ½ H2O + CaSO4+ 2H2O
B. Reaction between CaSO4+ 2H2O and water
C. Nucleation and growth of CaSo4 ½ H2O crystals
D. Reaction between hemihydrate and hihydrate
The hygroscopic technique is associated with______________?
A. Investment
B. Hydrocolloids
C. Amalgam
D. Silicate
The product, which is obtained by calcining gypsum under steam pressure at 120-130°C or by dehydrating gypsum in the presence of sodium succinate is_______________?
A. Alpha – hemihydrates
B. Beta – hemihydrates
C. Calcium sulphate dihydrate
D. Orthorhombic anhydrate
A rough / Chalky surface of the cast is due to_______________?
A. Not waiting for 20 min before pouring
B. High speed accelerator
C. Air incorporation in the mix
D. All of the above
The most commonly used accelerator in gypsum product is___________________?
A. Sodium fluoride
B. Potassium fluoride
C. Potassium sulfate
D. Aluminium sulfate
The strength of the gypsum specimen when the water in excess of that required for the hydrate of the hemihydrate is left in the specimen is called____________?
A. Dry strength
B. Green strength
C. Water strength
D. Compressive strength
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