251. Which one of the following non-metals is not a poor conductor of electricity? [IAS 2007]
     (a) Sulphur
     (b) Selenium
     (c) Bromine
     (d) Phosphorus
Ans: (b)
252. Which one of the following types of glass can cut off ultraviolet rays? [IAS 2007]
     (a) Soda glass
     (b) Pyrex glass
     (c) Jena glass
     (d) Crookes glass
Ans: (d)
253. Which one among the following is called philosopher"s wool? [IAS 2007]
     (a) Zinc bromide
     (b) Zinc nitrate
     (c) Zinc oxide
     (d) Zinc chloride
Ans: (c)
254. Which one of the following does not contain silver? [IAS 2007]
     (a) Horn silver
     (b) German silver
     (c) Ruby silver
     (d) Lunar caustic
Ans: (b)
255. Consider the following chemicals :
     1) Benzene
     2) Carbon tetrachloride
     3) Sodium Carbonate
     4) Trichloroethylene
     Which of the above is/are used as dry cleaning chemicals? [IAS 2006]
     (a)  1only
     (b)  2 only
     (c)  1, 2 and 4
     (d)  1, 2, 3 and 4
Ans: (d)
256. Match the following: [CDS 2010]
     Item                    Toxic Substance
     A. CFL lamp             1. Nitrogen oxides
     B. Automobile battery 2. Phthalates
     C. Polymer              3. Lead
     D. Diesel engine        4. Mercury
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