When a white color powder, P is added to a colorless liquid, Q, then bubbles of a gas R is
coming out along with a hissing sound. When the gas R is passed through an another
solution S, it turns milky white.
i) Identify P, Q, R and S
ii) Explain why solution S is turned milky when gas R is passed through it, write both
the word equation and chemical equation to support your answer.
b) What happens when magnesium oxide is dissolved in water? What is the action of this
solution on litmus paper?
pls answer fast
Answers
Explanation:
Zinc carbonate (A) is the white amorphous solid which on heating gives colourless gas (B) which is carbon dioxide and the residue (C) which is zinc oxide.
ZnCO
3
Δ
B
CO
2
+
C
ZnO
Carbon dioxide gas turns lime water milky and zinc oxide is yellow when hot and white when cold.
Zinc oxide dissolves in dilute HCl to form zinc chloride which reacts with potassium ferrocyanide to form white ppt.
Zinc carbonate dissolves in dil HCl to liberate carbon dioxide gas (B).
ZnCO
3
+2HCl→ZnCl
2
+H
2
O+CO
2
↑
Ammonium hydroxide neutralizes excess HCl.
Zn(II) ions react with hydrogen sulphide to give a white ppt D which is ZnS.
Zn
2+
+S
2−
→ZnS↑
Zn(II) ions react with NaOH to form white precipitate E which is zinc hydroxide.
Zn
2+
+2NaOH→
white ppt, E
Zn(OH)
2
This ppt dissolves in excess NaOH
white ppt, E
Zn(OH)
2
+2NaOH→
sodium zincate
Na
2
ZnO
2
+2H
2
0