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⁞ Chemistry

General Science ➤ Chemistry ➤ 2
Question 26
Q26.  What is the mass of one mole of a substance in grams is called?
 

Answer :  Molecular Mass


Molecular mass is a number equal to the sum of the atomic masses of the atoms in a molecule. The molecular mass gives the mass of a molecule relative to that of the 12C atom, which is taken to have a mass of 12. Molecular mass is a dimensionless quantity.
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Question 27
Q27.  Which of the following metals can deposit copper from copper sulphate solution?
 

Answer :  Iron


The iron displaces copper from its salt, to make iron sulfate solution and deposit a thin coating of metallic copper on the surface of the metal. In general, any metal higher than copper in the “electromotive series” will displace copper from copper sulfate solution or any other copper salt solution.
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Question 28
Q28.  The gas causing acid rain in an industrial area is:
 

Answer :  Sulphur dioxide


The main gases responsible for causing acid rain are sulphur dioxide as well as nitrous oxides. The main sources of sulphur dioxide are metal working industries and coal-fired power stations whereas nitrous oxide is from vehicles and fuel combustion.
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Question 29
Q29.  Bronze is an alloy of:
 

Answer :  Copper & tin


Bronze is an alloy consisting primarily of copper, commonly with about 12% tin and often with the addition of other metals (such as Aluminium , Manganese, Nickel or Zinc) and sometimes non-metals or metalloids such as arsenic, phosphorus or silicon. These additions produce a range of alloys that may be harder than copper alone, or have other useful properties. It was particularly significant in antiquity so much that bronze age was named after that alloy.
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Question 30
Q30.  Chemical composition of cement is:
 

Answer :  Limestone, Clay and Gypsum


The two important raw materials used for the preparation of cement are :

  • Limestone : CaCO3 is used in the manufacture of cement just to provide CaO.
  • Clay : Clay is hydrated aluminium silicate and iron (iii) oxide having chemical formula Al2O3SiO2Fe2O3.2H2O. Thus, clay consists of aluminium oxide (Al2O3), silicon dioxide (SiO2), and iron (iii) oxide (Fe2O3) along with water molecules.

In addition of limestone and clay, gypsum is also used during preparation of cement. It is added into the cement to slow down the setting of cement when water is added into it.
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