HSC Science (Electronics) 12th Standard Board Exam - Maharashtra State Board Important Questions

Sucrose decomposes in acid solution into glucose and fructose according to the first order rate law with `t_(1/2)` = 3 hours. What fraction of the sample of sucrose remains after 8 hours?

Write the reactions involved in the zone of reduction in blast furnace during extraction of iron.

The rate constant for a first order reaction is 100 s^–1. The time required for completion of 50% of reaction is _______.

(A) 0.0693 milliseconds

(B) 0.693 milliseconds

(C) 6.93 milliseconds

(D) 69.3 milliseconds

Silica is added to roasted copper ore during smelting process to remove _______.

(A) ferrous sulphide

(B) ferrous oxide

(C) cuprous sulphide

(D) cuprous oxide

Define Hydrometallurgy?

Explain refining of nickel by Mond process.

What is the process in which concentrated ore is reduced to the corresponding metal by heating at high temperature with a reducing agent?

(a) Polling                      

(b) Pyrometallurgy

(c) Hydrometallurgy

(d) Calcination

Sucrose decomposes in acid solution to give glucose and fructose according to the first order rate law. The half life of the reaction is 3 hours. Calculate fraction of sucrose which will remain after 8 hours.

Write chemical formulae of the following ores :

(a) Calamine 

(b) Haematite                     

(c) Magnetite

(d) Corundum

Write the reactions involved in extraction of silver from its ore by leaching process.

For a first order reaction, show that time required for 99% completion is twice the time required for the completion of 90% of reaction.

 A first order reaction takes 40 minutes for 30% decomposition. Calculate t_1/2 for this reaction. (Given log 1.428 = 0.1548)

Fe₂O₃ is reduced to spongy iron near the top of blast furance by

(A) H₂

(B) CaO

(C) SiO₂

(D) CO

Mention names and formulae of two ores of alumunium.

Draw neat and labelled diagram of Bessermer converter used in the extraction of copper.

The rate of reaction for certain reaction is expressed as:

`1/3(d[A])/dt=-1/2(d[B])/dt=-(d[C])/dt`

 The reaction is ______.

A first order reaction takes 23.1 minutes for 50% completion. Calculate the time required for 75% completion of this reaction.

(log 2 = 0.301, log 3 = 0.4771, log 4 = 0.6021)

MnO₂ and Ca₃(PO₄)₂ present in iron ore get reduced to Mn and P in the zone of _______.

(A) combustion

(B) reduction

(C) fusion

(D) slag formation

Explain magnetic separation process of ores with the help of a neat, labelled diagram.

Define Leaching.