1. Why do gold and silver not corrode in moist air?
2. Why does the colour of heated copper become black when air is passed over it?
3. Why do we protect iron articles by applying painting on them?
4. A chemical change cannot be normally reversed why?
5. A silver spoon is kept immersed in an aqueous copper sulphate solution then what change will take place?
6. Why does not copper liberate hydrogen on reacting with dilute sulphuric acid?
Answers
Answer:
hey here is your answer
1) Gold and silver are the least reactive metals in the rectivity series, hence can not bond with oxygen easily. Therefore they both can not get corroded easily.
2) The color of the heated copper powder becomes black when air is passed over it because of its reaction with oxygen i.e. air. When it reacts with oxygen it forms copper oxide which is black in color. ... Yet again, if air is passed over copper, the metal will get oxidized again, forming black copper oxide.
3) Iron articles are painted to prevent them from rusting. After painting iron surface does not come in contact with moisture and air which cause rusting.
4) Chemical change cannot be reversed back because products so formed in a chemical reaction are totally different from the reactants. a chemical change cannot be normally reversed because in a chemical reaction,a new substance is formed with the help of the processes like heating,baking,etc.
5) When a silver spoon is immersed in a copper sulphate solution, nothing happens. It is because silver is less reactive than copper according to the electrochemical series, so it can not displace copper from copper sulphate solution. However copper would have replaced silver if the case was opposite.
6) Copper does not reacts with dilute sulphuric acid, liberating hydrogen because copper is lower in the electromotive series than hydrogen. A more reactive element can displace a less reactive element from its salt solution. ... The metals below hydrogen in the activity series cannot do that.
hope it help you
Answer:
1).Answer
Both silver and gold metals are very little reactive or they are Noble metals. Their surface do not corrode in moist air.
2). Answer
On passing year over heated copper powder, the oxygen present reacts with copper to form copper (lI) oxide which has a black colour.
3). Answer
When according of paint for oil is given on the surface of iron articles, moisture does not stick to it. In absence of water, iron does not get rusted. Thus, surface of the article remains protected.
4). Answer
A chemical change is always accompanied by chemical reaction in which the bones in the reactants break and newborns in the product are formed. The change is permanent and cannot normally reversed.
5). Answer
No change will take place and the silver spoon will remain unaffected. Moreover blue colour of copper sulphate will also not fade. This is because of the reason that no chemical reaction takes place between silver and copper sulphate solution as silver is placed below copper in the reactivity series.
6). Answer
Copper is placed below hydrogen in the reactivity series. Therefore, it cannot loss electrons to hydrogen ions of the acid. Hydrogen gas is not evolved when copper reacts with dilute sulphuric acid.