Vii Bronze
Give reasons.?
Give reasons.
(i) The silver jewellery turns black after sometime.
(ii) A bronze statue turns green after sometime
(iii) An aqueous solution of acid conducts electricity.
(iv) While diluting an acid. It is recommended that acid should be added to water, not water to the acid.
(v) Blue colour of copper sulphate crystals disappears on heating
(vi) Lead nitrale gives brown fumes on heating
(vii) Blue colour of copper sulphate solution is destroyed when Iron filings are added to it.
1) Silver oxidizes in air, and silver oxide is black
2) Bronze contains copper, which oxidizes for form green copper (II) oxide (like statue of liberty)
3) Acids dissociate to form ions in solution. The ions are electrically charged and will carry an electric current.
4) Combining acid and water generates heat, which can cause the acid to spatter. When acid is added to water, the acid/water solution starts out very dilute, and so does not generate much as much heat, reducing risk of spattering.
5) The blue color is actually due to a hydrate of copper sulfate. Heating drives off the water, which generates white copper sulfate, losing the blue color.
6) The brown fumes are NO2 gas, which forms in an oxidation-reduction reaction when lead nitrate is heated.
7) Iron reduces copper ions in the copper sulfate to copper metal. The copper sulfate solution is blue, so when all the copper ions in the solution have been reduced, the blue color will be gone.
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