17.

Find the percentage composition of roseo-cobaltic chloride. (Co Cl. 10NH,. H2O.)

18. 07 gram of cobalt gave 292-3 c.c. of hydrogen measured over water at 20° C. and 756 m.m.

atomic weight of the metal?

Co+ 2HCl = CoCl ̧ + H ̧.

What is the

19. How many cubic centimetres of nickel (▲ 8.8) will a spherical balloon of gold-beater's skin, 50 c.m. across, weighing 5 grams, and filled with hydrogen just not lift?

20. A substance contains cobalt 26.69 per cent., arsenic 25 per cent., oxygen 21:31 per cent., and water 24 per cent. What is its formula?

21. 14 grams of impure cobalt were dissolved in acid and mixed with potassium acetate and nitrate. The precipitate dried at 100° C. weighed 9.2 grams. What percentage of cobalt was there in the substance taken?

2CoC1, + 2HCH ̧0, +12KNO, +0 = 4KCl + H2O

3

2

+2KC2H2O2+ Co2K ̧ (NO2)12°

22. If a cubic foot of water weighs 62.4 lbs., find the diameter in inches of a cast-iron (▲ 7·25) 32 lb. cannon-ball.

CHAPTER XXXIII.

CHROMIUM. Cr= 52.

1. FIND the percentage composition of chrome ironstone (Cr2O,FeO).

2. How many grams of sodium in vapour must be passed over 147 grams of heated chromic chloride to reduce it to chromium?

3. Find the percentage composition of chromic oxide (Cr2O3).

4. 10 grams of chromium trioxide when heated left 7.6 grams of chromic oxide. What is the atomic weight of chromium?

5. How much is lost by 100 grams of lead chromate when heated in a stream of hydrogen?

2PbCrO,+5H2 = 2Pb+ Cr2O2+5H2O.

4

6. According to Berlin 100 parts of lead nitrate give 97.576 parts of lead chromate; find the atomic weight of chromium.

Pb2NO, + K,CrO, 2KNO, + PbCrO

3

7.

43 grams of chromium trioxide are heated to 250° C. What volume of oxygen at that temperature is evolved?

8. The three most elevated buildings in Europe are (a) the Hospice de St Gotthardt 2075 m., (B) the Hospice de St Bernard 2491 m., (y) the Observatory on Mount Etna 2942 m. above sea-level. Find each of these altitudes in feet.

9. How many tons of potassium dichromate can be made from 10 tons of chrome ironstone?

2FeOCг ̧ ̧+3K,CO2 + CaO + 70 = 3K,CrO ̧ + CaCro

4

4K,CrO4 + 2H2SO̟ ̧ = 2K„SO + 2H„O + 2K„Cr2O„.

4

10. What is the percentage composition of chromium phosphide (CrP)?

11. 163 grams of chromic oxide are heated with charcoal; how much chromium is formed, and what volume of carbon monoxide at 26° C. is evolved?

Cr2O2+30=3CO + 2Cr.

12. A substance contains chromic oxide 54.67 per cent., and water 45.33 per cent. Find its formula.

13. What volume of oxygen is given off on heating 2.98 grams of potassium dichromate with hydrogen sulphate?

2K ̧Cr2O,+ 10H2SO1 = 4HKSO1 + 2Cr ̧3SO2+ 8H ̧0 + 60.

7

4

2

14. How many times heavier than air is the vapour of chromium hexafluoride (CrF)?

15. Find the percentage composition of potassium chloro-chromate (KCICRO).

16. What volume of hydrogen at 15° C. is required to reduce 100 grams of chromic to chromous chloride?

Cr Cl+2H2HCl + 2CrCl ̧.

17. According to Péligot, 100 grams of chromous chloride (CrCl) contain 57.5 grams of chlorine. Find the atomic weight of chromium.

18. How much chromic sulphide can be obtained from 100 grams of chromic oxide, and what volume of carbon dioxide at 210° C. is given off?

2CrO2+3CS, 2Cr ̧§ ̧ + 3CO,.

=

2

19. The vapour of 20 c.c. of chromyl dichloride (▲ 1·7) is passed through a red-hot tube; how much chromic oxide, and what volume of oxygen at 6o C. and of chlorine at 6o C. is evolved?

20. A substance contains potassium 19.84 per cent., chromium 39.57 per cent., and oxygen 40.58 Find its formula.

per cent.

21. What volume of sulphur dioxide at 15o C. and 780 m.m. is required to reduce 47 grams of potassium dichromate?

K ̧Cr ̧O, + 3SO, + H2SO̟ ̧ = K2SO ̧ + Cr ̧3SO ̧ + H ̧0.

2

2

4

4

4

22. A substance contains potassium 27.07 per cent., chromium 12 per cent., carbon 16·62 per cent., and 44.31 per cent. Find its formula.

oxygen

23. How much chromyl dichloride can be obtained by distilling 23 grams of sodium chloride with potassium dichromate and hydrogen sulphate?

4NaCl + K ̧Cr ̧O, + 3H2SO1 = 2Na ̧SO̟ + K2SO̟

2

7

4

24. How much potassium dichromate must be heated with hydrogen sulphate to make 15 litres of oxygen at 15° C. ?

K ̧Cr ̧0, + 5H2SO̟ ̧ = 2HKSO ̧ + Cr ̧3S0 ̧ + 4H ̧0 + 30.

2 7

25. 100 grams of mercurous chromate are heated; how much chromic oxide is formed, and what volume of oxygen is given off?

2Hg,CrO1 = 4Hg + Cr ̧O ̧ + 50.

2 3

26. What volume of oxygen at 30° C. is given off on heating 70 grams of chromium trioxide?

27. What volume of nitrogen at 150° C. is given off on heating 10 grams of ammonium dichromate?

(NH), Cr2O, = Cr2O ̧ + 4H2O + 2N.

2 7

2 3

2

28. What volume of hydrogen sulphide at 10° C. is required to reduce 100 grams of chromium trioxide?

2CrO2+3H,S=3H,0 + 3S+ Cr2O..

2

29. What volume of chlorine at 30° C. is given off on distilling 1 gram of chromium trioxide with hydrogen chloride ?

2CrO2+ 12HCl = 6H2O + Cr2Cl ̧ + 6C1.

30. 20 grams of potassium dichromate are heated with