Advertisements
Advertisements
Question
Explain why, the surface of some metals acquires a dull appearance when exposed to air for a long time.
Advertisements
Solution
Most of the metals are reactive towards air. They react with oxygen present in the air to form metal oxides. The metal oxide formation appears on the surface of the metals as a thin layer. This thin layer formation of metal oxide on the metallic surface causes the dull appearance of the metals. Thus, the surface of some metals acquires a dull appearance when exposed to air for a long time.
RELATED QUESTIONS
Show the formation of Na2O by the transfer of electrons.
State whether the following statement is true or false:
Non-metals react with dilute acids to produce a gas which burns with a ‘pop’ sound.
What changes in the colour of iron nails and copper sulphate solution do you observe after keeping the iron nails dipped in copper sulphate solution for about 30 minutes?
Name two metals which form amphoteric oxides.
Write an equation for the reaction of:
Sodium with oxygen
Ordinary aluminium strips are not attacked by water because of the presence of a layer of ______ on the surface of aluminium.
Which of the following elements would yield an acidic oxide.
Na, S, C, K, H
What type of oxides are formed when metals combine with oxygen? Explain with the help of an example.
How do non-metals react with hydrogen? Explain with an example.
What happens when calcium reacts with chlorine? Write an equation for the reaction which takes place
A copper plate was dipped in AgNO3 solution. After certain time, silver from the solution was deposited on the copper plate. State the reason why it happened. Give the chemical equation of the reaction involved.
You are given samples of three metals − sodium, magnesium and copper. Suggest any two activities to arrange them in order of their decreasing reactivities.
What is meant by the reactivity series of metals? Arrange the following metals in an increasing order of their reactivities towards water:
Zinc, Iron, Magnesium, Sodium
One of the following is not a neutral oxide. This is:
(a) CO
(b) H2O
(c) N2O
(d) Na2O
Which one of the following four metals would be displaced from the solution of its salt by the other three metals?
(a) Zn
(b) Ag
(c) Cu
(d) Mg
Which of the following reactions will not occur? Why not?
(a) MgSO4 (aq) + Cu (s) → CuSO4 (aq) + Mg (s)
(b) CuSO4 (aq) + Fe (s) → FeSO4 (aq) + Cu (s)
(c) MgSO4 (aq) + Fe (s) → FeSO4 (aq) + Mg (s)
Rewrite the following statement by selecting the correct option.
A solution of Al2(SO4)3 in water is _____________.
Metals are generally hard. Which of the following metals is an exception and can be cut with a knife?
Which of the following property is not responsible for copper to be used as electrical conduction wires?
