Page 163 - Chemistry ICSE Class IX

Study of the First Element : Hydrogen 151

Aim: dŽ ĚĞŵŽŶƐƚƌĂƚĞ ƌĞĂĐƟŽŶ ŽĨ ĐĂůĐŝƵŵ ǁŝƚŚ ǁĂƚĞƌ͘ ZĞƉŽƌƚ LJŽƵƌ ŽďƐĞƌǀĂƟŽŶƐ ĂŶĚ ǁƌŝƚĞ ĞƋƵĂƟŽŶ ĨŽƌ ƚŚĞ ƌĞĂĐƟŽŶ͘
ACTIVITY 2 Procedure:

ƒ dĂŬĞ ĨĞǁ ƉŝĞĐĞƐ ŽĨ ĐĂůĐŝƵŵ ŵĞƚĂů ŝŶ ƚŚĞ ĐŽŶŝĐĂů ŇĂƐŬ ĂŶĚ
ĂƌƌĂŶŐĞ ƚŚĞ ĂƉƉĂƌĂƚƵƐ͕ ĂƐ ƐŚŽǁŶ ŝŶ ƚŚĞ ĂĚũŽŝŶŝŶŐ ĮŐƵƌĞ͘

ƒ WĂƐƐ ƚŚĞ ŐĂƐ ĞǀŽůǀĞĚ ƚŚƌŽƵŐŚ ƐŽĂƉ ƐŽůƵƟŽŶ͘ ƵďďůĞƐ ĂƌĞ
ƒ ƌŽƉ ĚŝůƵƚĞ ƐƵůƉŚƵƌŝĐ ĂĐŝĚ ĨƌŽŵ Ă ĚƌŽƉƉŝŶŐ ĨƵŶŶĞů͘
ĨŽƌŵĞĚ͘
ƒ ƌŝŶŐ Ă ďƵƌŶŝŶŐ ŵĂƚĐŚƐƟĐŬ ŶĞĂƌ ƚŚĞ ŐĂƐͲĮůůĞĚ ďƵďďůĞƐ͘
ObservaƟon: tŚĞŶ ƚŚĞ ďƵƌŶŝŶŐ ŵĂƚĐŚƐƟĐŬ ŝƐ ďƌŽƵŐŚƚ ŶĞĂƌ ƚŚĞ
ŐĂƐͲĮůůĞĚ ďƵďďůĞƐ͕ ƚŚĞ ŐĂƐ ďƵƌŶƐ ǁŝƚŚ Ă ƉŽƉ ƐŽƵŶĚ͘
Conclusion: Ɛ ƚŚĞ ŐĂƐ ďƵƌŶƐ ǁŝƚŚ Ă ƉŽƉ ƐŽƵŶĚ͕ ŝƚ ŝƐ ŚLJĚƌŽŐĞŶ ŐĂƐ͘
ZĞĚƵĐƟŽŶ
Room
;ŝŝͿ Ă;sͿ н Ϯ, K;lͿ o Ă;K,Ϳ Ϯ н , Ϯ ;gͿ
Ϯ
ƚĞŵƉ͘
ĂůĐŝƵŵ ŚLJĚƌŽdžŝĚĞ
KdžŝĚĂƟŽŶ ;ůŝŵĞ ǁĂƚĞƌͿ
ĂůĐŝƵŵ
By the action of water on metal hydrides
Hydrides of alkali and alkaline earth metals react readily with water
producing hydrogen.
CaH (s) + 2H O(l) o Ca(OH) (aq) + H (g)
2
2
2
2
calcium hydride water (cold) calcium hydroxide hydrogen gas
Preparation of hydrogen from acids
Acids contain replaceable hydrogen. Electropositive metals, such as sodium,
potassium, zinc, iron, aluminium, and magnesium, which appear above
hydrogen in the electrochemical series displace hydrogen from acids. For
example,
Zn + H SO (aq) o ZnSO (aq) + H (g)
4
2
2
4
zinc sulphuric acid (dil.) zinc sulphate hydrogen
Mg + H SO (aq) o MgSO (aq) + H (g)
4
4
2
2
magnesium sulphuric acid (dil.) magnesium sulphate hydrogen ů ĚŽĞƐ ŶŽƚ ƌĞĂĐƚ ǁŝƚŚ Ěŝů͘ , ^K ͘
4
Ϯ
Al(s) + H SO (l) o No reaction
4
2
aluminium sulphuric acid (dil.)
Fe(s) + H SO (l) o FeSO 4 + H (g)
4
2
2
iron sulphuric acid (dil.) ferrous sulphate hydrogen EŝƚƌŝĐ ĂĐŝĚ ŵĂŬĞƐ ƚŚĞ ŵĞƚĂůƐ ƉĂƐƐŝǀĞ
ďLJ ĨŽƌŵŝŶŐ Ă ůĂLJĞƌ ŽĨ ŽdžŝĚĞ ŽŶ ƚŚĞŝƌ
Action of hydrochloric acid on Mg, Al, Zn, and Fe ƐƵƌĨĂĐĞƐ͘ ^Ž͕ ŝƚ ŝƐ ŶŽƚ ƵƐĞĚ ŝŶ ƐƵĐŚ
Mg + 2HCl(aq) o MgCl 2 + H (g) hydrogen displacement reacƟons͘
2
magnesium hydrochloric acid magnesium chloride hydrogen
2Al + 6HCl(aq) o 2AlCl (aq) + 3H (g)
3
2
aluminium hydrochloric acid aluminium chloride hydrogen
Zn + 2HCl o ZnCl 2 + H (g)
2
zinc hydrochloric acid (dil.) zinc chloride hydrogen
Fe + 2HCl o FeCl 2 + H (g)
2
iron hydrochloric acid (dil.) ferrous chloride hydrogen
Preparation of hydrogen from alkalis
Action of NaOH on metals
Metals like zinc, aluminium, tin, etc. or a nonmetal like silicon when
boiled with concentrated solution of sodium hydroxide (or caustic soda) or
potassium hydroxide (or caustic potash) produce hydrogen.