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The metallic constituents of hard water are

A. Calcium, magnesium and iron

B. Magnesium, Calcium and tin

C. Magnesium, tin and iron

D. Iron, tin and calcium

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  1. Which of the following elements is obtained from sea weeds ?
  2. In an atomic nucleus, neutrons and protons are held together by
  3. Apparatus invented by Archimedes is :
  4. The most important ore of Aluminium is
  5. Earth's seasons are caused by which of the following?
  6. Permanent hardness of water, due to sulphates of the metal, can be destroyed by the use of
  7. The colour of Emerald is
  8. Which of the following is in liquid form at room temperature ?
  9. Glass is made from the mixture of
  10. Brass gets discoloured in air due to the presence of which gas in air
  11. The oxide of Nitrogen used in medicine as anaesthetic is
  12. The metal that is present in Photo Films is
  13. Which of the following items will be attracted to the north pole of a permanent magnet by a magnet force?
  14. What is the unit for measuring the pitch or frequency of sound ?
  15. Water has maximum density at
  16. The element present in the largest amount in rocks and minerals is
  17. The Panda belongs to the same family as that of
  18. The metal used in storage batteries
  19. Polythene is industrially prepared by the polymerisation of
  20. The type of glass used in making prisms and lenses is
  21. Which of the following elements is non-radioactive?
  22. The recent atomic weight scale is based on
  23. The metallic constituents of hard water are
  24. The fastest acting enzyme in the biological kingdom is
  25. Carbon tetrachloride fire extinguisher should not be used in closed room because it produces poisonous…
  26. The formula of Plaster of Paris is
  27. The speed of light with the rise in the temperature of the medium
  28. Which of the following is commonly called a polyamide ?
  29. The accumulation of stress along the boundaries of lithospheric plates results in which of the following?
  30. The property of a substance to absorb moisture from the air on exposure is called