30.   Which of the following compound is tetrahedral?
    (a) ammonia
    (b) carbon tetrachloride
    (c) water
    (d) acetylene
Ans: (b)
31. Which one of the following polymeric materials is used for making bulletproof jackets? [JPSC (Pre) 2011]
    (a) Nylon 6,6
    (b) Rayon
    (c) Kevlar
    (d) Dacron
Ans: (c)
32. The nucleus of a singly ionized carbon atom contain- [NDA 2012]
    (a) 6 protons and 6 neutrons
    (b) 5 protons and 6 neutrons
    (c) 6 protons, 6 neutrons and 6 electrons
    (d) 12 protons, 6 neutrons and 6 electrons
Ans: (a)
33. Which one among the following nitrogen compounds has the least percentage of nitrogen by mass? [NDA 2012]
    (a) (NH4)3 PO4
    (b) NH3
    (c) NH4OH
    (d) NH4NO3
Ans: (b)
34. Which one among the following is the correct order of amount of lime (CaO), Silica (SiO2), Alumina (AI2O3) and
         ferric oxide (Fe2O3) in Portland cement? [NDA 2012]
         (a) CaO > SiO2 > AI2O3 > Fe2O3
         (b) SiO2> CaO > Fe2O3 > AI2O3
         (c) AI2O3 > SiO2 > CaO > Fe2O3
         (d) Fe2O3 > AI2O3 > SiO2 > CaO
Ans: (a)
35. Which one among the following is the major constituent of soda lime glass? [NDA 2012]
         (a) sodium oxide
         (b) calcium oxide
         (c) calcium carbonate
         (d) silica
Ans: (b)
36. In which of the following chlorine has + 1 oxidation number? [CDS 1999]
         (a) hypochlorous acid
         (b) hydrochloric acid
         (c) zinc chloride
         (d) chlorine
Ans: (a)
37. Which of the following is not a metallic mineral? [JPSC (Pre) 2011]
         (a) haematite
         (b) bauxite
         (c) gypsum
         (d) limonite
Ans: (d)
38. Which of the following does not pollute? [MPPCS (Pre) 2011]
         (a) copper
         (b) cadmium
         (c) arsenic
         (d) Nickel
Ans: (a)
39. The element whose oxidation state in its every compound is same is : [CDS 2002]
         (a) carbon
         (b) fluorine
         (c) hydrogen
         (d) oxygen
Ans: (b)