Chemistry

Chemical Compounds and Reactions

329 Questions

Chemical compounds and reactions involve understanding the properties, colors, and formation of various chemical substances. Questions focus on identifying precipitates, observing color changes during reactions, and naming common compounds. This topic is a fundamental part of the chemistry syllabus for competitive exams.

identifying precipitateschemical reaction colorscompound namingcolloidal particle propertiesacid base reactions

Chemical Compounds and Reactions Questions

Multiple choice chemistry d and f block elements coloured complexes magnetic nature of transition metals general characteristics of first transition series

Which one of the following forms a colorless solution in aqueous medium?

  1. ${Cr}^{3+}$
  2. ${Ti}^{3+}$
  3. ${Sc}^{3+}$
  4. ${V}^{3+}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$Cr^{3+}$ = $3d^3$ = coloured

$Ti^{3+}$ =  $3d^1$ = coloured

$V^{3+}$ =  $3d^2$ = coloured

$Sc^{3+}$ has electron configuration of [Ar] $4s^0  3d^0$. Therefore without any unpaired electrons it forms a colorless solution in aqueous medium. 

Multiple choice chemistry nature of matter heterogenous mixture - colloidal solution and its properties suspensions and colloids mixtures

Colloidal solutions of metals like gold can be prepared when their salt solutions react with certain substances like $SnCl _{2}$, formaldehyde, phenyl hydrazine, etc.
2$AuCl _{3}$ + 3$SnCl _{2}$ $\rightarrow$ 3$SnCl _{4}$ + $2Au _{sol}$
The above method is an example of:

  1. reduction method

  2. oxidation method

  3. hydrolysis method

  4. double decomposition method
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  • A colloid is a heterogeneous system in which one substance is dispersed (dispersed phase) as very fine particles in another substance called dispersion medium.
  • Colloidal solutions of metals like gold can be prepared when their salt solutions react with certain substances like $SnCl _2$, formaldehyde, phenylhydrazine.
In the given reaction,
$2AuCl _3 + 3SnCl _2 \rightarrow 3SnCl _4 + 2Au _{sol}$
The oxidation state of $Sn$ is changing from -2 to -4. So,it is gaining electrons and hence the method is the reduction method.

Multiple choice chemistry nature of matter heterogenous mixture - colloidal solution and its properties suspensions and colloids mixtures

The nature of colloidal solution obtained when excess $Fe{ Cl } _{ 3 }$ is added in precipitate of $Fe{ \left( OH \right)  } _{ 3 }$?

  1. positively charged

  2. negatively charged

  3. no charge

  4. All of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Peptization takes place forming a positively charged colloidal sol of $Fe(OH) _3$
Peptization is a process of passing of a precipitate into colloidal particles on adding suitable electrolyte. The electrolyte added is known as peptizing agent. A few examples of sols obtained by peptization are given below:
A reddish brown colored colloidal solution is obtained by adding small quantity of ferric chloride solution to the freshly precipitated ferric hydroxide.
Multiple choice chemistry nature of matter heterogenous mixture - colloidal solution and its properties suspensions and colloids mixtures

When negatively charged colloid-like $As _2S _3$ sol is added to +vely charged $Fe(-OH) _3$ sol in suitable amounts:

  1. both the sols are precipitated simultaneously

  2. this process is called mutual coagulation

  3. they become positively charged colloid

  4. they become negatively charged colloid
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

When -vely charged colloid-like $As _2S _3$ sol is added to +vely charged $Fe(OH) _3$ sol in suitable amounts both the sols are precipitated simultaneously it is due to the fact that negatively charged particles of the arsenious sulphide sol take up positive ions, resulting neutralisation of the charge on the colloidal particles and hence lowering the stability of the sol and both precipitate simultaneously.

Multiple choice chemistry nature of matter heterogenous mixture - colloidal solution and its properties suspensions and colloids mixtures

In the preparation of AgI sol, the excess of $AgNO _{3}$ is added to potassium iodide solution. The particles of the sol will acquire:

  1. negative charge

  2. positive charge

  3. no charge

  4. unpredictable
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When AgNO3 is in excess, the AgI particles adsorb Ag+ ions from the solution, forming an AgI/Ag+ layer, which gives the colloidal particles a positive charge.

Multiple choice chemistry substances in common use chemical from common salt compounds of carbon some useful compounds in everyday life

Bleaching powder is effective with cold water, but ineffective with hot water. This is because of:

  1. oxidation of chloride radical

  2. reduction of chloride radical

  3. reduction of hypochlorite radical

  4. hydrolysis of hypochlorite radical
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Bleaching action takes place due to the hypochlorite radical [$ClO^{-}$].

But when used in hot water, hot water favours reduction of the hypochlorite radical as a result of which bleaching powder is ineffective with hot water.
Generally, Bleaching powder is used as a disinfectant widely.

Multiple choice chemistry substances in common use chemical from common salt compounds of carbon some useful compounds in everyday life

Bleaching powder is soluble in cold water giving a milky solution due to:

  1. available chlorine

  2. lime present in it

  3. calcium carbonate formation

  4. the absorption of carbon dioxide from atmosphere
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Bleaching powder on reaction with cold water form milky solution of calcium hydroxide. 

$CaOCl _2+H _2O\rightarrow Ca(OH) _2+Cl _2$

Thus because of the lime present in it, it gives a milky solution when dissolved in water.

Multiple choice chemistry substances in common use chemical from common salt compounds of carbon some useful compounds in everyday life

Bleaching powder is obtained by the interaction of $Cl _2$ with a:

  1. dilute solution of $Ca(OH) _2$
  2. concentrated solution of $Ca(OH) _2$
  3. dry $CaO$

  4. dry slaked lime
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$Ca(OH) _2 +Cl _2 \rightarrow Ca(OCl)Cl + H _2O$
Bleaching powder is obtained by the interaction of $Cl _2$ with a dry slaked lime.

Multiple choice chemistry substances in common use chemical from common salt compounds of carbon some useful compounds in everyday life

Bleaching powder slowly decomposes to form:

  1. $CaCl _2+Ca(ClO _3) _2$
  2. $CaO+Cl _2$
  3. $CaCl _2+Ca(OCl) _2$
  4. $CaCO _3+Cl _2$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When exposed to air, bleaching powder gives a smell of chlorine. This is because bleaching powder reacts with carbon dioxide from the atmosphere to produce calcium carbonate and chlorine.

$Ca(OCl) _2 +CO _2 \rightarrow CaCO _3 +Cl _2$

Multiple choice chemistry substances in common use chemical from common salt compounds of carbon some useful compounds in everyday life

The amount of chlorine obtained from a sample of bleaching powder by treatment with excess of dilute acid or $ \displaystyle CO _{2}$ is called available chlorine.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The available chlorine is defined as the percentage of chlorine made available by bleaching powder when treated with dilute acids. The available chlorine present in bleaching powder sample is determined iodometricaliy by treating its solution with an excess of potassium iodide solution in the acidic medium.