JEE Main Previous Year Papers Questions With Solutions Chemistry Metallurgy and Environmental Chemistry
1.The metal extracted by leaching with a cyanide is (2002)
1) Mg 2) Ag 3) Cu 4) Na
Ans.(2) Silver ore forms a soluble complex with 1
NaCl from which silver is precipitated using scrap zinc.
Ag2S + 2NaCN -> Na[Ag(CN)?]
2Na[Ag(CN)2] + Zn ->Na2[Zn(CN)4] + 2Ag
2.Aluminium is extracted by the electrolysis of (2002)
1) bauxite 2) alumina
3)alumina mixed with molten cryolite
Ans.(3) Alumina is mixed with cryolite in the extraction of aluminium metal. Addition of cryolite decreases the melting point and increases the conductivity.
3.Cyanide process is used for the extraction of (2002)
1) barium 2) aluminium
3) boron 4) silver
Ans.(4) Cyanide forms a soluble complex with silver. Finally Ag is precipitated using zinc.
4.When the sample of copper with zinc impurity is to be purified by electrolysis, the appropriate electrodes are (2002)
1)pure zinc pure copper
2)impure sample pure copper
3)impure zinc impure sample
4)pure copper impure sample
Ans.(4) Pure metal always deposits at cathode.
5.When rain is accompanied by a thunderstorm, the collected rain water will have a pH value (2003)
1)slightly higher than that when the thunderstorm is not there
2)uninfluenced by occurrence of thunderstorm
3)which depends on the amount of dust in air
4)slightly lower than that of rain water without thunderstorm
Ans.(4) The rain water after thrunderstorm contains dissolved acid and therefore the pH is less than rain water without thunderstorm.
6.Which one of the following ores is best concentrated by froth-floatation ? (2004)
1) Magnetite 2) Malachite
3) Galena 4) Cassiterite
Ans.(3) Galena is sulphide mineral. Sulphide minerals are usually concentrated by froth floatation method.
7.The smog is essentially caused by the presence of (2004)
1) 02 and 03 2) 03 and N2
3)Oxides of sulphur and nitrogen 4)02 and N2
Ans.(3) Smog is Smoke + Fog. Somg contains mainly S02 and NOx
8.During the process of electrolytic refining of copper, some metals present as impurity settle as ‘anode mud’. These are (2005)
1) Sn and Ag 2) Pb and Zn
3) Ag and Au 4) Fe and Ni
Ans.(3) Crude Cu contains Au and Ag as impurities.
9.Heating mixture of CuzO and Cu2S will give (2005)
1) Cu + S02 2) Cu + S03
3) CuO + CuS 4) Cu2S03
Ans.(1) Self-reduction occurs upon heating a mixture of oxide and sulphide of copper.
2Cu20 + Cu2S——- > 6Cu + S02
10.Identify the wrong statements in the following:(2008)
1)Chlorofluorocarbons are responsible for ozone layer depletion
2)Greenhouse effect is responsible for global warming
3)Ozone layer does not permit infrared radiation from the sun to reach the earth
4)Acid rains is mostly because of oxides of nitrogen and sulphur.
Ans.(3) Ozone layer does not allow ultraviolet radiation from sun to reach earth.
11.Which of the following factors is of no significance for roasting sulphide ores to the oxides and not subjecting the sulphide ores to carbon reduction directly ? (2008)
1)Metal sulphides are thermodynamically more stable than CS2
2)C02 is thermodynamically more stable than CS2
3)Metal sulphides are less stable than the corresponding oxides
4)C02 is more volatile than CS2
Ans.(1) Metal slphides are more stable to heat than carbon disulphide.
12. Which method of purification is represented by the following equation (2012)
Ans.(4) Titanium and zirconium are refined by vapour phase refining called Van Arkels method. Nickel is refined by Mond’s process.
13.The gas leaked from a storage tank of the Union Carbide plant in Bhopal gas tragedy was (2013)
1) Methylisocyanate 2) Methylamine
3) Ammonia 4) Phosgene
Ans.(1) It is called MIC gas.
14.Which series of reactions correctly represents chemical relations related to iron and its compound ? (2014)
15.Assertion (A) : Nitrogen and Oxygen are the main components in the atmosphere but these do not react to form oxides of nitrogen.
Reason (R) : The reaction between nitrogen and oxygen requires high temperature. (2015)
1)Both assertion and reason are correct, and the reason is the correct explanation for the assertion.
2)Both assertion and reason are correct, but the reason is the not correct explanation for the assertion.
3)The assertion is incorrect, but the reason is correct.
4)Both the assertion and reason are incorrect.
Ans.(1) N2 has triple bond and 02 has double bond.