Chemistry

Chemical Compounds and Reactions

505 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 further aspects of equilibria dissociation constants ionisation of weak acids and weak bases ionization constants of weak acids and weak bases

In the third group of qualitative analysis, the precipitating reagent is $NH {4}Cl + NH _{4} OH$. The function of $NH _{4}Cl$ is to______

  1. increase the ionization of $NH _{4} OH$
  2. suppress the ionization of $NH _{4} OH$

  3. stabilise the hydroxides of group cations

  4. convert the ions of group third into their respective chlorides
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Common ion effect is observed when a solution of weak electrolyte is mixed with a solution of strong electrolyte, which provides an ion common to that provided by weak electrolyte.


The NH4OH is weak base it does not ionises completely. Thus due to presence of common ion NH4+ in NH4Cl, it supresses the ionisation of weak base NH4OH in order to decrease the OH- concentration so that higher group cations will not get precipitated.

Thus the pair $NH _{4} OH + NH _{4} Cl$ shows common ion effect. 

Ammonium chloride suppresses the ionization of ammonium hydroxide.

Option B is correct.

Multiple choice group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

Observe the following statements.
I .Bleaching powder is used in the preparation of chloroform.
II. Bleaching powder decomposes in the presence of $\mathrm{C}\mathrm{o}\mathrm{C}1 _{2}$ to liberate $\mathrm{O} _{2}$.
III. Aqueous $\mathrm{K}\mathrm{H}\mathrm{F} _{2}$ is used in the preparation of fluorine.

  1. I,II and III are correct

  2. Only II is correct.

  3. Only I and III are correct

  4. Only I and II are correct.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Molten $KHF _{2}$ is used in the preparation of fluorine.

Rest two statements are true.

Multiple choice group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

Which of the following will displace the halogen from the solution of of halide
a $) Br _{2}$ added to an $NaCl$ solution
$\mathrm{b}) Cl _{2}$ added to a $KBr$ solution
$\mathrm{c}) Cl _{2}$ added to an $NaF$ solution
$\mathrm{d}) Br _{2}$ added to to a $KI$ solution
Find the correct answer :

  1. a, b, c

  2. b, c

  3. b, d

  4. all are correct
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$Br^{-}$ can reduce $Cl _{2}$ to $Cl^{-}$ $(E _{cell}=+ve)$

$I^{-}$ can reduce $Br _{2}$ to $Br^{-}$ $(E _{cell}=+ve)$

$E _{cell}=+ve$ in both case

$\therefore$ Reaction is feasible

Multiple choice group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

Iodine can be obtained from NaI solution by the action of:

  1. chlorine

  2. bromine

  3. soluble chloride

  4. soluble bromine
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

The iodine can be obtained by reacting chlorine or bromine by NaI. This is because the electronegativity of chlorine and bromine is more than the iodine and also the reactivity of chlorine and bromine is more than the iodine.

Multiple choice group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

When a dry solid is treated with a mild oxidizing agent, a purple solid is produced. What is the dry solid?

  1. $N _2$
  2. $KI$
  3. $CCl _4$
  4. $AgNO _3$
  5. $CaCO _3$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A purple solid (iodine) is produced by treatment of the dry solid $KI$ with a mild oxidizing agent. The mild oxidising agent oxidizes iodide ion to iodine.

Multiple choice group 17 elements - trends in chemical properties group 17 elements - properties p- block elements-ii p-block elements chemistry

Treatment of the dry solid with a mild oxidizing agent produces a purple solid having formula _______.

  1. $N _2$
  2. $KI$
  3. $CCl _4$
  4. $AgNO _3$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Iodine can be displaced from potassium iodide if a more reactive element is made to react with potassium iodide. In the presence of a mild oxidising agent, the iodine ions are oxidised to $I _2$. Iodine is purple in colour.

Multiple choice chemistry production of metals extraction of metal from concentrated ore basics of metallurgy extraction of metals from ore

Extraction of chlorine from brine is based on:

  1. reduction

  2. displacement

  3. oxidation

  4. evaporation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
In the extraction of chlorine by electrolysis of brine, oxidation of ${ Cl }^{ - }$ ion to chlorine gas occurs.
$2{ Cl }^{ - }+2{ H } _{ 2 }O\rightarrow 2{ OH }^{ - }+{ H } _{ 2 }+{ Cl } _{ 2 }$
Multiple choice chemistry energy rocks and minerals petroleum and natural gas fossil fuels

The RON/MON value of iso-octane is:

  1. $0$
  2. $100$
  3. $50$
  4. $1000$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Octane number can be determined by RON, MON and AKI. The most common method used for the measurement is RON. RON is determined by running the fuel in a test engine and comparing the results with those for mixtures of iso-octane and $n$- heptane. The RON/MON values of iso-octane is 100.

Multiple choice chemistry energy rocks and minerals petroleum and natural gas fossil fuels

Which of the following aromatic compound is not obtained from reformate during cracking?

  1. Xylene

  2. Toluene

  3. Cummene

  4. Benzene
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Cracking is a process of refining or extraction of crude oil. In this process heat and pressure is used to break, rearrange or combine hydrocarbon molecules. In this process more the depth of cracking, lower octane number of gasoline are obtained. Cummene is not obtained during cracking.