Page 118 - Chemistry ICSE Class X

104 ICSE Chemistry – 10
Action of Sodium Hydroxide on Ammonium Salts

Ammonium salts are the salts of weak base ammonium hydroxide. It
decomposes when treated with strong alkalis. With sodium hydroxide,
ammonium chloride (a typical ammonium salt) gives ammonia gas and
sodium chloride. The reaction goes faster on heating.
warm
NH Cl(s) + NaOH(aq) o NH (g) + NaCl(aq) + H O(l)
3
2
4
ammonium chloride sodium hydroxide ammonia gas
The evolved ammonia gas can be tested by bringing a glass rod dipped
in hydrochloric acid near the mouth of the test tube, when white fumes are
formed around the glass rod.
ASSIGNMENT 1

Colour of the salts and their solutions, Action of
sodium hydroxide and ammonium hydroxide on certain metallic salt solutions

ϭ͘ EĂŵĞ ƚŚĞ ƚLJƉĞ ŽĨ ĐŚĞŵŝĐĂů ĂŶĂůLJƐŝƐ ǁŚŝĐŚ ŝŶǀŽůǀĞƐ ŝĚĞŶƟĮĐĂƟŽŶ ŽĨ ƚŚĞ ĐŽŶƐƟƚƵĞŶƚƐ ŽĨ Ă ƐƵďƐƚĂŶĐĞ͘
Ϯ͘ tƌŝƚĞ ƚŚĞ ƉƌŽďĂďůĞ ĐŽůŽƵƌ ŽĨ ƚŚĞ ĨŽůůŽǁŝŶŐ ƐĂůƚƐ͗
;ĂͿ /ƌŽŶ;//Ϳ ƐƵůƉŚĂƚĞ
;ďͿ /ƌŽŶ;///Ϳ ĐŚůŽƌŝĚĞ
;ĐͿ WŽƚĂƐƐŝƵŵ ŶŝƚƌĂƚĞ
;ĚͿ ĂůĐŝƵŵ ŽdžŝĚĞ
;ĞͿ ůƵŵŝŶŝƵŵ ƐƵůƉŚĂƚĞ
ϯ͘ EĂŵĞ ƚŚĞ ƉƌŽďĂďůĞ ĐĂƟŽŶ ƉƌĞƐĞŶƚ ŝŶ ĞĂĐŚ ŽĨ ƚŚĞ ĨŽůůŽǁŝŶŐ ƐŽůƵƟŽŶƐ͗
;ĂͿ ůƵĞͲĐŽůŽƵƌĞĚ ƐŽůƵƟŽŶ
;ďͿ WŝŶŬͲĐŽůŽƵƌĞĚ ƐŽůƵƟŽŶ
;ĐͿ zĞůůŽǁͲĐŽůŽƵƌĞĚ ƐŽůƵƟŽŶ
;ĚͿ ůƵŝƐŚͲŐƌĞĞŶ ĐŽůŽƵƌĞĚ ƐŽůƵƟŽŶ
ϰ͘ EĂŵĞ ƚŚĞ ƉƌŽďĂďůĞ ĂŶŝŽŶ ƉƌĞƐĞŶƚ ŝŶ ĞĂĐŚ ŽĨ ƚŚĞ ĨŽůůŽǁŝŶŐ ƐŽůƵƟŽŶƐ͗
;ĂͿ WƵƌƉůĞ ;ďͿ zĞůůŽǁ ;ĐͿ KƌĂŶŐĞ
ϱ͘ EĂŵĞ ĮǀĞ ĐĂƟŽŶƐ ǁŚŝĐŚ ĨŽƌŵ ĐŽůŽƵƌůĞƐƐ ƐĂůƚƐ͘

Action of Alkalis on Certain Metals
Certain metals, such as zinc, lead and aluminium, react with hot
concentrated strong alkalis (such as NaOH and KOH) forming their soluble
salts and liberating hydrogen.
ƒ Reaction of zinc with hot and concentrated NaOH and KOH
Zn(s) + 2NaOH(aq) o Na ZnO (aq) + H (g)
2
2
2
zinc hot and conc. sodium zincate hydrogen
Zn(s) + 2KOH(aq) o K ZnO (aq) + H (g)
2
2
2
zinc hot and conc. potassium zincate hydrogen
ƒ Reaction of lead with hot and concentrated NaOH and KOH
Pb(s) + 2NaOH(aq) o Na PbO (aq) + H (g)
2
2
2
lead hot and conc. sodium plumbite hydrogen
(colourless)
Pb(s) + 2KOH(aq) o K PbO (aq) + H (g)
2
2
2
lead hot and conc. potassium plumbite hydrogen
(colourless)