31. Potassium nitrate is used in
A. medicine
B. fertiliser
C. salt
D. glass
32. Permanent hardness of water may be removed by the addition of
A. sodium carbonate
B. alum
C. potassium permanganate
D. lime
33. Soda water contains
A. carbonic acid
B. sulphuric acid
C. carbon dioxide
D. nitrous acid
34. The most important ore of aluminium is
A. galena
B. calamine
C. calcite
D. bauxite
35. Most soluble in water is
A. camphor
B. sulphur
C. common salt
D. sugar