911. The working time of polycarboxyletecement can be prolonged by all of the following, except ?
A. using a cool glass slab
B.cooling the polyacrylic acid liquid in a refrigerator
C.cooling the powder in a refrigerate,
D.none of the above

912. Which of the following it not an ingredient of gypsum bonded investments?
A. Alpha hemihydrate
D.Boric acid
E.None of the above

913. The polymerization of heat-curing resin Is Initiated by the formation of?
A. hydrogen bonds
B.free redicals
C. Valance electrons
D. active atoms

914. Equilibrium phase diagrams are useful in determining the?
A. solubility of the alloy components at a particular temperature
B.chemical composition of the alloy at a particular temperature
C.melting point and boiling point of an alloy
D.stability of the alloy at a particular temperature

915. A gold alloy, designated as 750 fine, indicates that?
A.7.5% of the alloy is pure gold
B.the alloy is 20 karat
C. three-fourth of the alloy is pure gold
D. the grain size of the alloy is 75 microns
E. the alloy has been distilled 750 times


916. A potentially toxic element in base metal alloys is?
A. molybdenum

917. Thermal shrinkage of heat curing resins is, that shrinkage which occurs?
A. during the polymerization of the resin
B.on cooling, from glass transition temperature to room temperature
C.on cooling, from boiling point to mouth temperature
D.on cooling, from curing temperature to glass transition temperature

918. A method of expressing the degree of polymerization of polymers is by?
A. average atomic weight
B. valence electrons
C.stoitiometric ratio
D. number average molecular

919. For which of the following cements is polyacrylic acid the parent compound?
A. calcium hydro-oxide cements
B.Copper phosptrate cements
C.Glass ionomer cements
D.Polycarboxylate cements

920. All of the following are problems associated with electric annealing of gold pellets, except?
A. the various pellets cannot stick together
B.it is difficult to anneal the appropriate amount of gold required
C.air currents may affect the uniformity of heating
D.there is a greater chance of contamination if the gold is not used immediately