COMPOUNDS OF CHLORINE. 414. How does hydrochloric acid occur in nature, and by what other names is it known? 415. How may hydrochloric acid be prepared from its elements? Describe different ways of effecting the union. 416. Starting with common salt, how could you prepare hydrochloric acid? 417. A burning jet of hydrogen is plunged into a jar of chlorine; what occurs, and what property does the product possess which distinguishes it from both hydrogen and chlorine? 418. Using only chlorine and water, how may hydrochloric acid be prepared? 419. What occurs when a galvanic current passes through a strong solution of hydrochloric acid, previously saturated with chlorine? 420. In what proportions by volume and weight do hydrogen and chlorine unite? 421. What volume of hydrogen at N.T. P. is needed to unite with 1 gramme of chlorine? 422. A cylinder contains a mixture of equal volumes of hydrogen and chlorine, it is opened under a solution of potassium iodide. State what occurs, and express the reaction by an equation. 423. Describe various methods which may be used to ascertain the proportion of hydrogen and chlorine contained in hydrochloric acid gas. 424. Give several reactions to show the tendency of chlorine to unite with combined hydrogen. 425. How much hydrochloric acid must be decomposed to yield enough chlorine to liberate 2'34 grammes of iodine from potassium iodide? 426. A solution of hydrochloric acid required 10'67 grammes of silver nitrate to precipitate it completely. Find the volume of hydrochloric acid (at N.T.P.) in solution. 427. Sketch the apparatus required for preparing small quantities of pure hydrochloric acid, and calculate the quantities of common salt and sulphuric acid required to saturate a litre of water with the gas (water at 15° C. dissolves 450 times its bulk of the gas). 428. How is hydrochloric acid prepared on the large scale? Sketch the plant required. 429. What impurities are usually present in commercial hydrochloric acid, and how is their presence accounted for? 430. At 12° C. and 760 m.m. pressure I gramme water absorbs 0762 gramme hydrochloric acid. Find the quantity of salt and sulphuric acid required to yield a ton of hydrochloric acid at the same temperature and pressure. 431. What important fact was ascertained by Roscoe and Dittmar on distilling aqueous solutions of hydrochloric acid at different pressures? How may this property be applied to the preparation of standard solutions of the acid? 432. What occurs when a current of hydrochloric acid is passed over (a) sodium, (b) manganese dioxide, (c) iron? 433. How is iodine chloride prepared, and what are its properties? 434. If a current of chlorine be led into solution of potassium iodide mixed with starch, the liquid at first becomes blue, but by the continued passage of the gas it becomes colourless. Explain this. 535. Give the names and formulæ of the oxides of chlorine, and state how each is prepared. 436. What occurs when a red-hot wire is placed in a tube filled with chlorine tetroxide? 437. Give several illustrations of the powerful oxidizing action of chlorine tetroxide? 438. What is euchlorine, and how is it prepared? 439. Write the names and formulæ of the compounds containing chlorine, hydrogen, and oxygen. 440. Give three distinct methods for the preparation of hypochlorous acid. What are the properties of the substance? 441. Compare the bleaching action of chlorine with that of hypochlorous acid, and explain each by equations. 442. What happens when lime is thrown into a cylinder containing chlorine? What is the common name of the substance produced, and how is it obtained on the large scale? 443. Express by equations the action on bleaching powder of (a) sulphuric acid, (b) nitric acid, (c) hydrochloric acid. 444. What occurs when a stream of chlorine is passed through (a) a hot solution of potash, (b) a cold solution of potash? Express each reaction by an equation. 445. How is potassium chlorate prepared on the large scale? How would you react on calcium chlorate so as to obtain potassium chlorate? 446. How is potassium chlorate separated from potassium chloride when both are present in a solution? By what tests could you distinguish the two salts? 447. How is potassium perchlorate obtained from the chlorate? Give an equation. 448. A certain weight of potassium chlorate is heated for the preparation of perchlorate; 10 litres of oxygen at N.T. P. are obtained. Find the weight of chlorate used and of perchlorate obtained. 449. How did Roscoe obtain pure perchloric acid, and what are its properties? 450. What compound does perchloric acid form with water, and how is it obtained? How is its formation explained? |