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NCERT Class X Science Class: Chapter β 3. Metals and Nonmetals β Part-9
Question 50:
A non-metal A is an important constituent of our food and forms two oxides B and C. Oxide B is toxic whereas C causes global warming
- Identify A, B and C
- To which Group of Periodic table does A belong?
Answer:
- A is carbon, B is carbon monoxide and C is carbon dioxide
- A belongs to Group β 14 of the Periodic table
Question 51:
Give two examples each of the metals that are good conductors and poor conductors of heat respectively.
Answer:
- Good conductor: Silver (Ag) and Copper (Cu) .
- Poor conductor: Mercury (Hg) and Lead (Pb) :
Question 52:
Name one metal and one non-metal that exist in liquid state at room temperature. Also name two metals having melting point less than
Answer:
Following are the metals and non-metals, which exist in liquid state at room temperature.
Metal β Mercury (Hg)
Non-metal β Bromine (Br)
Two metals with melting points less than are Cesium and Gallium
Question 53:
An element A reacts with water to form a compound B which is used in white washing. The compound B on heating forms an oxide C which on treatment with water gives back B. Identify A, B and C and give the reactions involved.
Answer:
Element A is calcium (Ca) . When it reacts with water, it forms calcium hydroxide. Thus, compound B is calcium hydroxide , which is used in white washing.
Therefore,
Compound B on heating gives
Thus, C is calcium oxide
on treatment with water gives back .
Question 54:
An alkali metal A gives a compound B on reacting with water. The compound B gives a soluble compound C on treatment with aluminium oxide. Identify A, B and C and give the reaction involved.
Answer:
For A:
Alkali metals are sodium, potassium, lithium etc.
On reacting with water, they give metal hydroxide.
Hydroxide molecular mass
As molecular mass of the metal hydroxide is 40, n = 1 or 2, and correspondingly the molecular mass of metal is 23 or 6.
That is metal A is either sodium or lithium
For B:
Sodium hydroxide or lithium hydroxide. Lithium hydroxide - molecular mass is not 40
Therefore metal A is Sodium: Na and compound B is sodium hydroxide.
Therefore,
Therefore, compound B is sodium hydroxide
For C:
Sodium hydroxide reacts with aluminium oxide to give sodium aluminate Thus, C is sodium aluminate . The reaction involved is
Question 55:
Give the reaction involved during extraction of zinc from its ore by
- Roasting of zinc ore
- Calcination of zinc ore
Answer:
Extraction of zinc is shown in below figure:
For (A) :
The roasting is the process of burning of a ore in the presence of the excess air.
Therefore, the zinc sulphide will be heated with excess of the air.
The following reaction will be performed
For (B) :
Whereas, the calcination is the process of heating of a ore in the absence of the oxygen,
Therefore, this will perform the following reaction.
Question 56:
A metal M does not liberate hydrogen from acids but reacts with oxygen to give a black colour product. Identify M and black coloured product and also explain the reaction of M with oxygen.
Answer:
Metal m is copper which does not liberate when it reacts with acid as copper is least reactive than Hydrogen. Therefore, it cannot displace hydrogen from .
Copper reacts with oxygen to form copper (II) oxide, which is black in colour