Advertisements
Advertisements
प्रश्न
Explain why, the surface of some metals acquires a dull appearance when exposed to air for a long time.
Advertisements
उत्तर १
Some metals, when exposed to air for a long time, react with oxygen in the atmosphere to form a dull layer of metal oxide on their surfaces. This makes the metals look dull.
उत्तर २
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.
APPEARS IN
संबंधित प्रश्न
Iron is
(a) More reactive than zinc
(b) More reactive than aluminium
(c) Less reactive than copper
(d) Less reactive than aluminium
‘E’ is an element which reacts with oxygen to form an oxide E2O. An aqueous solution of E2O turns red litmus blue, so:
i. What is the nature of oxide E2O ?
ii. Write the name of element ‘E’.
Write the chemical reaction when iron reacts with dilute H2SO4.
Show the formation of Na2O by the transfer of electrons.
An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be:
Name the metal which has been placed at the top of the reactivity series.
Which of the two metals is more reactive: copper or silver?
Write equation for the reaction of magnesium with oxygen.
Complete and balance the following equation:
Fill in the following blank with suitable word:
The white powder formed when magnesium ribbon burns in oxygen is of ....................
Why does aluminium not react with water under ordinary conditions?
Why is white phosphorus kept immersed under water?
What is the action of water on magnesium ? Write equation of the chemical reaction involved.
An element X reacts with hydrogen, when heated, to form a covalent hydride H2X. If H2X has a smell of rotten eggs, the element X is likely to be:
(a) carbon
(b) sulphur
(c) chlorine
(d) phosphorus
A metal less reactive and another metal more reactive than hydrogen are:
(a) aluminium and lead
(b) iron and magnesium
(c) copper and tin
(d) copper and mercury
What is the cause of chemical bonding (or chemical combination) of atoms of elements?
Write a chemical equation to illustrate the use of aluminium for joining cracked railway lines.
Explain the following:
Reactivity of aluminium decrease if it is dipped in nitric acid.
Which one among the following is an acidic oxide?
Why is acidified water considered to be a good conductor of electricity?
