Tag: chemistry

Questions Related to chemistry

Octane number is a scale for counting?

chemistry energy rocks and minerals petroleum and natural gas fossil fuels

  1. the quantity of water present in alcohol.

  2. the percentage of liquefied petroleum gas in a given sample of petrol.

  3. the quality of petrol

  4. the number of different hydrocarbons present in a sample of petrol.

Show answer
Correct Option: C
Explanation:

Octane rating or octane number is a standard measure of the performance of a motor- or aviation fuel. The higher the octane number, the more compression the fuel can withstand. fuels with a higher octane rating are used in high performance petrol engines that require higher compression ratios. thus it reflects the quality of fuel.

Quality of a diesel is measured in terms of its?

chemistry energy rocks and minerals petroleum and natural gas fossil fuels

  1. Cetane number

  2. Octane number

  3. Gold number

  4. Avogadro number

Show answer
Correct Option: A
Explanation:

A cetane number is the measure of the quality of the diesel . Higher cetane number indicates that the fuel ignites more readily when sprayed over hot compressed air.

Which of the following is present in the heavy oil obtained during petroleum distillation ?

chemistry energy rocks and minerals petroleum and natural gas fossil fuels

  1. Gas oil

  2. Fuel oil

  3. Diesel oil

  4. All of these

Show answer
Correct Option: D
Explanation:

The following fuels are present in the heavy oil obtained during petroleum distillation 1. Gas oil  2.Fuel oil and Diesel oil.

So all the given options are correct.

Hence option D is correct.

Complete removal of ______ from gasoline is done by Unisol process using caustic soda and methyl alcohol. 

chemistry energy rocks and minerals petroleum and natural gas fossil fuels

  1. asphalt

  2. mercaptans

  3. diolefins

  4. waxes

Show answer
Correct Option: B
Explanation:

Unisol process is a regenerative method for not only extracting or removing mercaptans but also some of the nitrogen compounds. In this process first gasoline is washed counter-currently with aqueous caustic methanol solution. The spent caustic is regenerated in a stripping tower where the methanol, water and mercaptans are extracted.

The electrical process of coating an inexpensive conductor with a metal is called electroplating.

chemistry chemical effects of electric current applications of electrolysis electroplating extraction of metals by electrolysis

  1. True

  2. False

Show answer
Correct Option: A
Explanation:
Electroplating is a process that uses electric current to deposit/reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode.

It is used to coat a relatively mundane metal, such as copper, with a thin layer of another, more precious metal, such as gold or silver. 

Hence, option $\text{A}$ is correct.

Chromium plating is done to make the object scratch proof and appear shiny.

chemistry chemical effects of electric current applications of electrolysis electroplating extraction of metals by electrolysis

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Chromium plating is a technique of electroplating in which a thin layer of chromium is coated onto a metal object. The layer is decorative (shiny), provide corrosion resistance, ease cleaning procedures, and increase surface hardness (scratch resistance).


Hence, option A is correct.

The process of depositing a thin layer of desired metal over another metal by passing an electric current through some electrolyte is called :

chemistry chemical effects of electric current applications of electrolysis electroplating extraction of metals by electrolysis

  1. electric shielding

  2. electric polishing

  3. electric coating

  4. electroplating

Show answer
Correct Option: D
Explanation:

Electroplating is the application of electrolytic cells in which a thin layer of metal is deposited onto an electrically conductive surface.


Hence, option D is correct.

Rate constant in case of first order reaction is :

chemistry chemical kinetics dependence of reaction rate on concentration of reactants order of reactions factors influencing rate of a reaction

  1. Inversely proportional to the concentration units

  2. Independent of concentration units

  3. Directly proportional to concentration units

  4. Inversely proportional to the square of concentration units

Show answer
Correct Option: B
Explanation:

For First order of reaction,
$Rate= k [A]$,


$k = \cfrac {mol/L}{sec\times {mol/L}}=sec^{-1}$

Option B is correct.

Fill in the blanks by choosing the correct option;
Order of the reaction is the $X$ of the powers to which concentration terms are raised in experimentally determined rate equation. The unit of first order rate constant is $Y$. The unit of first order rate constant when concentration is measured in terms of pressure and time in minutes is $Z$.

chemistry chemical kinetics dependence of reaction rate on concentration of reactants order of reactions factors influencing rate of a reaction

  1. $X\rightarrow product, Y\rightarrow mol\ L^{-1} time^{-1}, Z\rightarrow atm\ min^{-1}$

  2. $X\rightarrow sum, Y\rightarrow L\ mol^{-1}time^{-1}, Z\rightarrow atm\ min^{-1}$

  3. $X\rightarrow product, Y\rightarrow L\ mol^{-1}, Z\rightarrow atm\ min^{-1}$

  4. $X\rightarrow sum, Y\rightarrow time^{-1}, Z \rightarrow min^{-1}$

Show answer
Correct Option: D
Explanation:

The order of a chemical reaction is defined as the sum of the powers of the concentration of the reactants in the rate equation of that particular chemical reaction.


General formula for the unit of rate constant = mole$^{(1-n)}$ L$^{(n-1)}$ min$^{-1}$.

For 1$^{st}$ order reaction, 
n = 1
Therefore, unit of rate constant $=$ min$^{-1}$

The unit of rate constant in terms of pressure and time:
  mol $^{( 1-n)}$  L $^{ (n-1)}$ min$^{ -1 }$ or  atm$^{( 1-n) }$ min $^{ -1 }$


For 1$^{st}$ order reaction, 
n = 1
Therefore, the unit is min$^{-1}.$

Hence, the correct answer is option $\text{D}$.

Match the rate law given in column I with the dimensions of rate constant given in column II and mark the appropriate choice.

Column I Column II
(A) $Rate = k[NH _{3}]^{0}$ (i) $mol\ L^{-1} s^{-1}$
(B) $Rate = k[H _{2}O _{2}][I^{-}]$ (ii) $L\ mol^{-1} s^{-1}$
(C) $Rate = k[CH _{3}CHO]^{3/2}$ (iii) $s^{-1}$
(D) $Rate = k[C _{2}H _{5}Cl]$ (iv) $L^{1/2} mol^{-1/2} s^{-1}$
chemistry chemical kinetics dependence of reaction rate on concentration of reactants order of reactions factors influencing rate of a reaction

  1. $(A)\rightarrow (iv), (B) \rightarrow (iii), (C)\rightarrow (ii), (D) \rightarrow (i)$

  2. $(A)\rightarrow (i), (B) \rightarrow (ii), (C)\rightarrow (iii), (D) \rightarrow (iv)$

  3. $(A)\rightarrow (ii), (B) \rightarrow (i), (C)\rightarrow (iv), (D) \rightarrow (iii)$

  4. $(A)\rightarrow (i), (B) \rightarrow (ii), (C)\rightarrow (iv), (D) \rightarrow (iii)$

Show answer
Correct Option: D
Explanation:
(A) $Rate= k[NH _3]^0$
It is zero order reaction.
$\therefore$ Units of rate constant are same as rate.
i.e $ mol\ l^{-1}s^{-1}$

(B) $Rate=k[H _2O _2]^1[I^-]^1$
It is second order reaction as order $=1+1=2$
$\therefore$ Units of Rate constant are $L \ mol^{-1}s^{-1}$

(C) $Rate=k[CH _3CHO]^{3/2}$
It is fractional order reaction with order $= \cfrac 32$
$\therefore$ Units of rate constant are $L^{\cfrac 12}mol^{-\cfrac 12}s^{-1}$

(D) $Rate=k[C _2H _5Cl]^{-1}$
It is first order reaction. So units of rate constant are $s^{-1}$