136.Why does extraction pose a potential safety problem?

a)the equipment becomes pressurized and often explodes(正确答案)

b)hazardous organic solvents are always necessary

c)the equipment becomes pressurized and may suddenly pop open if not handled properly,spraying hazardous chemicals into the air

137.When must you wear chemical splash goggles?

a.When working with non-hazardous chemical buffers.(正确答案)

b.When working with corrosive acids,poison or other hazardous material.

c.When working with compressed gas.

d.When outside the splash zone of hazardous chemicals.

138.A researcher is working in lab where hazardous liquid chemicals are present.Which of the following is not considered appropriate personal protective equipment for this situation?

a.Open toed shoes.

b.Lab coat.

c.Chemical resistant gloves.

d.Chemical splash goggles.(正确答案)

139.The desire to maintain a safe laboratory environment for all begins with（）?

a.prevention(正确答案)

b.ubiquity

c.microbiology

d.accidents

140.Good work practices include,

a.smelling and tasting chemicals

b.not washing hands before and after lab

c.confining long hair and loose clothing

d.using damaged equipment and glassware.(正确答案)

141.While conducting a dangerous experiment,there should be operators.

A.one

B.two or more(正确答案)

C.three or more

142.Which of the following items is not a highly toxic chemical?

A.Potassium cyanide(KCN)

B.Sodium azide(NaN3)

C.Thallium(Tl)

D.Methanal(HCHO)(正确答案)

143.In what direction should we evacuate after a hazardous chemical accidents?

A、downwind

B、upwind(正确答案)

144.What are the unit of LD50 for acute toxicity of hazardous chemicals?

A.mg/kg(正确答案)

B.g/kg

C.mL/kg