Chemistry
Which metal is preferred for preparing hydrogen from:
(a) cold water?
(b) hot water?
(c) steam?
Write balanced equation for each case.
Hydrogen
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Answer
(a) Calcium is preferred for preparing hydrogen from cold water as the reaction is less vigorous than Sodium.
Ca + 2H2O ⟶ Ca(OH)2 + H2 ↑
(b) Magnesium reacts with boiling water and forms a base, magnesium hydroxide, liberating hydrogen gas.
Mg + 2H2O ⟶ Mg(OH)2 + H2 ↑
(c) Zinc is preferred for preparing hydrogen from steam. When steam is passed over heated zinc, hydrogen is liberated and zinc is converted to zinc oxide.
Zn + H2O ⟶ ZnO + H2 ↑
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Related Questions
(a) Where does Hydrogen occur in free state?
(b) How did the name 'hydrogen' originate?
Hydrogen can be prepared with the help of cold water. Give a reaction of hydrogen with:
(a) a monovalent metal
(b) divalent metal
Hydrogen may be prepared in the laboratory by the action of a metal with an acid.
(a) Which of the metals copper, zinc, magnesium or sodium would be the most suitable?
(b) Which of the acids dilute sulphuric, concentrated sulphuric, dilute nitric and concentrated nitric would you choose? Explain why you would not use the acids you rejected.
(c) How would you modify your apparatus to collect dry hydrogen? Which drying agent would you employ for this purpose?
Why are the following metals not used in the lab. preparation of hydrogen?
(a) calcium
(b) iron
(c) aluminium
(d) sodium