Important Paper Olympaid NSO Scinece

1. A metal is used for making electrical wires and cables. Its ore is concentrated by froth floatation method. If this metal is left in the air for some time, it gets corroded by developing a greenish deposit on it. Which metal are we talking about ?
(a) Zn                                                           
(b) Fe
(c) Cu                                                 
(d) Sn                                                   
Ans (c)
2. What is common among the ores of different metals ?
(a) They are all oxides                                           
(b) They are all sulphides
(c) They are all minerals                                       
(d) Both (a) & (c)                             
Ans (c)
3.  Few statements about the metals given below and matched with the metals. Mark the incorrect match.
(a) A metal used in joining electric wires - Magnesium
(b) A metal whose oxide is amphoteric - Zinc
(c) A metal unreactive towards oxygen and dilute acids - Gold
(d) A metal extracted by using electrolytic reduction – Aluminium                                                           
Ans (a)
4.  A non-metal X is an important constituent of our food. It forms two oxides Y and Z. Y is toxic and causes suffocation and even death while Z is responsible for global warming. Identify X, Y and Z.
(a) X = C, Y = CO, Z = CO2                                      
(b) X =S, Y = SO2, Z = SO3
(c) X = P, Y = P2O3, Z = P2O5                               
(d) X = O, Y = O2, Z = O3                                 
Ans (a)
5.   Identify the element that is relatively brittle.
(a) Sulphur                                                             
(b) Diamond
(c) Iron                                                                   
(d) Magnesium                                                
Ans (a)
6. 10 mL of freshly prepared iron sulphate was taken in four test tubes each. Strips of copper, iron, zinc and aluminium were introduced in these tubes. Which of the metals will show reaction ?
(a) Copper and Zinc                                                   
(b) Aluminium and copper
(c) Iron and aluminium                                            
(d) Zinc and aluminium                                 
Ans (d)
7.  A yellow coloured brittle element on burning produces a gas. The solution of this gas in water turns blue litmus red. The oxide is generally responsible for acid rain and for spoiling the building made of marble. The element and the oxide respectively are :
(a) Fe, Fe2O3                                                            
(b) Si, SiO2
(c) S, SO2                                                                     
(d) Ca, CaO                                                        
Ans (c)
8.   Latin name for X is ‘royal water’. It is a mixture of Y and Z in the ratio 3 : 1. Some of the properties of X are different from Y and Z. What are X, Y and Z respectively ?
(a) Aqua regia, HCl, HNO3                                         
(b) Aqua regia, HNO3, HCl
(c) H2SO4, H2O, SO2                                                   
(d) H2SO4, H2S, SO3                                         
Ans (a)
9.   Ethene is produced when :
(a) Ethanol reacts with ethanoic acid in presence of few drops of conc. H2SO4
(b) Ethanol is oxidized with acidified potassium dichromate
(c) Ethanol is heated with excess of conc. H2SO4 at 443 K
(d) Ethanol reacts with sodium metal                         
Ans (c)
10.   Rasika mixed sugarcane juice with yeast and kept in covered and sealed pot for a few days. After opening the pot she noticed that the juice started giving a strong smell. She filtered the juice and filled it in bottles. What is the name of the process and what is the product formed ?
(a) Fermentation, Ethyl alcohol                                                 
(b) Decomposition, Glucose
(c) Esterification, Fructose                                         
(d) Fermentation, Acetic acid                    
Ans (a)
 
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