1. Alkali metals do not exist in free state in nature because these are

2. The reason for floating of ore particles during concentration by froth floatation process is that

3. Which of the following metals is never found in free state?

4. An important constituent of amalgam is

5. Which of the following barium salts is soluble in water?

6. Which of the following carbonate decomposes on heating?

7. Duralumin is an alloy of aluminium with

8. Mixture of Mg${\mathrm{Cl}}_2$and MgO is called

9. The approximate percentage of gypsum in Portland cement is

10. In the preparation of sodium carbonate(${\mathrm{Na}}_2{\mathrm{CO}}_3)$which of the following is used as raw material?

11. The principle ore of aluminium is

12. Froth floatation process is used for the concentration of

13. A fire due to burning of lithium, sodium and potassium can be extinguished by

14. One of the constituents of the german silver is

15. Rocky impurities present in a mineral are called

16. An important mineral for magnesium is

17. One of the most important uses of quick-lime is

18. Sulphide ores are generally concentrated by