219. Which one of the following pairs of metals constitutes the lightest metal and the heaviest metal, respectively? [IAS
     (a) Lithium and mercury
     (b) Lithium and osmium
     (c) Aluminium and osmium
     (d) Aluminium and mercury
Ans: (b)
220. Flint glass is obtained from which of the following? [NDA 2008]
     (a) Zinc and barium borosilicate
     (b) Sand, red lead and potassium carbonate
     (c) Sodium aluminium borosilicate
     (d) Pure silica and zinc oxide
Ans: (b)
221. Which one of the following correctly defines the state of glass? [NDA 2008]
     (a) Crystalline solid
     (b) Super cooled liquid
     (c) Condensed gas
     (d) Liquid crystal
Ans: (b)
222. Match the following: [NDA 2008]
     Substance added                   Colour imparted to glass
     A. Chromium (III) oxide           1. Red
     B. Cobalt (II) oxide              2. Violet
     C. Cuprous oxide                  3. Green
     D. Manganese dioxide              4. Blue
           A         B         C       D
     (a)   2         1         4       3
     (b)   3         4         1       2
     (c)   3         1         4       2
     (d)   2         4         1       3
Ans: (b)
223. Which one of the following is an element which never exhibits positive oxidation state in any of its compounds? [NDA
     (a) Oxygen
     (b) Chlorine
     (c) Fluorine
     (d) Carbon
Ans: (c)
224. Which of the following statements with regard to Isotopes and Isobars is/are correct? [NDA 2008]
           1) Isotopes have same mass number.
           2) Isobars have same atomic number.
     (a) 1 only