HSC Science (Computer Science) 12th Standard Board Exam - Maharashtra State Board Important Questions for Chemistry

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.

The unit of rate constant for zero order reaction is _______.

(A) t^–1

(B) mol dm^–3 t^–1

(C) mol^–1 dm³ t^–1

(D) mol^–2 dm⁶ t^–1

Calcium carbonate used in the extraction of iron acts as _______.

(A) oxidising agent

(B) reducing agent

(C) gangue

(D) flux

Write the names and chemical formulae of any ‘two’ minerals of aluminium.

Mention the names of various steps involved in the extraction of pure metals from their ores.

Explain the following term

Flux

Which among the following reactions is an example of a zero order reaction?

a) `H_(2(g)) + I_(2(g)) -> 2HI_(g)`

b) `2H_2O_(2(l)) -> 2H_2O_(l) + O_(2(g))`

c) `C_12H_22O_(11(aq)) + H_2O_(l) -> C_6H_12O_(6(aq)) + C_6H_12O_(6(aq))`

d) `2NH_(3g)`   `N(2g) + 3H_(2(g))`

Which among the following minerals does NOT contain aluminium?

(a) Cryolite

(b) Siderite

(c) China clay

(d) Corundum

Explain the following methods to protect metals from corrosion:

Galvanization

Explain the following methods to protect metals from corrosion:

Passivation

Which one of the following oxidation state of Manganese is unstable?

(a) + 2

(b) + 4

(c) + 5

(d) + 7