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

Water samples (X and Y) from two different sources were brought to the laboratory for the measurement of dissolved oxygen (DO) using modified Winkler method. Samples were transferred to 300 ml BOD bottles. 2 ml of MnSO4 solution and 2 ml of alkaliodide-azide reagent were added to the bottles and mixed. Sample X developed a brown precipitate, whereas sample Y developed a white precipitate.

In reference to these observations, the correct statement is

  1. Both the samples were devoid of DO.

  2. Sample X was devoid of DO while sample Y contained DO.

  3. Sample X contained DO while sample Y was devoid of DO.

  4. Both the samples contained DO.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In the Winkler method, a brown precipitate (manganese hydroxide) indicates the presence of dissolved oxygen, while a white precipitate indicates the absence of dissolved oxygen.

Multiple choice chemistry solid state imperfections in solids

The incorrect statement is :

  1. When crystals of NaCI are heated in an atmosphere of sodium vapour, it appears yellow due to F-centres.
  2. $ O _2 $ is paramagnetic , $ CrO _2 $ is Ferromagnetic and $ MnO $ is anti-Ferromagnetic
  3. Certain oxides $ VO, VO _2VO _3 $ and $ TiO _3 $ show metallic properties at all temperatures.

  4. CCP & HCP have same coordination number.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The statement regarding VO, VO2, VO3, and TiO3 is incorrect because these oxides show metallic or insulating properties depending on the temperature, rather than metallic properties at all temperatures. The other statements correctly describe F-centres, magnetic properties, and close-packing structures.

Multiple choice chemistry solid state imperfections in solids

The presence of excess sodium in sodium chloride makes the crystal appearance yellow. This is due to the presence of

  1. Schottky defect

  2. Frenkel defect

  3. F-centres

  4. Interstitial defects
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When NaCl crystals are heated in sodium vapor, sodium atoms deposit on the surface and chloride ions diffuse to the surface to form NaCl. The remaining electrons occupy the anionic vacancies, creating F-centres, which absorb light and impart a yellow color.

Multiple choice chemistry solid state imperfections in solids

ZnO shows yellow colour on Heating due to:

  1. d-d transition

  2. C-T spectra
  3. Higher polarisation caused by $Zn^{2+}$ ion

  4. F-centres
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$ZnO$ shows yellow colour of heating due to F-centre

$ZnO\longrightarrow Zn^{2+}+2e^-+\cfrac{1}{2}O _2$
Electron get trapped in anion sites. This is called as F-centre. Due to F-centre colour of many compounds occurs.

Multiple choice chemistry d and f block elements imperfections in solids solid solutions formation of complex compounds and constituent of catalysts general characteristics of first transition series

Which of the following is not soluble in $NaOH$?

  1. $Fe(OH) _3$
  2. $Zn(OH) _2$
  3. $Al(OH) _3$
  4. $Sn(OH) _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Fe(OH)3 is a basic hydroxide and does not dissolve in NaOH. Zn(OH)2, Al(OH)3, and Sn(OH)2 are amphoteric and dissolve in strong bases like NaOH to form soluble complexes.

Multiple choice chemistry the d-and f-block elements imperfections in solids solid solutions formation of complex compounds and constituent of catalysts general characteristics of first transition series
Find the solid which has brilliant blue color.
  1. $Fe _2O _3$
  2. $CuSO _4$
  3. $NaBr$
  4. $KCl$
  5. $Ca(OH) _2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Copper sulphate $\displaystyle CuSO _4$ has brilliant blue color.
$Cu(II)$ ions with an outer electronic configuration of  $\displaystyle 3d^{9}$ have one unpaired electron. This results in blue colour which is due to $d-d$ transitions.

Multiple choice

After reaction with potassium iodide and copper sulphate, sodium thiosulphate solution is added. Find the incorrect statement about this reaction.

  1. Cu2I2 is formed.

  2. CuI2 is formed.

  3. Na2S2O3 is oxidised.

  4. Evolved I2 is reduced.

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When KI is added to the solution of cupper sulphate, an equivalent amount of I2 is liberated along with the formation white precipitate (of Cu2I2). This free iodine (I2), which remains in solution as [KI3] complex is then titrated with sodium thiosulphate solution using starch as indicator. At the end point of the titration, the blue colour of solution will disappear and a white precipitate of the Cu2I2 will remain in conical. The reactions that are taking place are:  

Multiple choice chemistry chemistry in everyday life common salt some useful compounds in everyday life salts and their properties

Which of the following imparts purple colour to glass?

  1. ${Cr} _{2}{O} _{3}$
  2. $Au{Cl} _{3}$
  3. ${Cu} _{2}O$
  4. $Mn{O} _{2}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 $MnO _2$which is black, is used to remove the green color from the glass and imparts purple tint to the glass. $Cr _2O _3$ imparts dark green colour, $Cu _2O$ produces a turquoise color, and $AuCl _3$ gives ruby red coloured glass.

Multiple choice chemistry chemistry in everyday life common salt some useful compounds in everyday life salts and their properties

Match the compounds /metal in $(X)$ with their uses in $(Y)$.

$X$ $Y$
$A.$ Liquid sodium metal $I.$ Breathing apparatus in submarine
$B.$ Potassium stearate $II.$ Explosive
$C.$ Potassium nitrate $III.$ Coolant in nuclear reaction
$D.$ Potassium superoxide $IV.$ Soft soap
  1. $A-I\, \quad\, B-III\, \quad\, C- II\, \quad\, D- IV$
  2. $A-III\, \quad\,B- IV\, \quad\,C- II\, \quad\, D- I$
  3. $A- II\, \quad\,B- I\, \quad\, C- III\, \quad\, D- IV$
  4. $A- IV\, \quad\, B- II\, \quad\, C- III\, \quad\,D- I$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

1. Liquid sodium metal is used as coolant in nuclear reaction
2. Potassium stearate is used in soft soap
3. Potassium nitrate is explosive
4. Potassium superoxide, which gives off oxygen as it absorbs carbon dioxide is used in Breathing apparatus in submarine

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

Colourless solution of silver nitrate is taken in two test tubes A and B. Metal plates of copper and platinum are dipped into test tubes, A and B respectively. Content of test tubes ____________.

  1. B turns green

  2. B turns blue

  3. A turns blue

  4. A remains colourless
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In test tube A, displacement reaction takes place as copper being more reactive displaces silver from silver nitrate solution thus leading to the formation of copper nitrate which is blue in colour. The chemical reaction can be written as:
$Cu + Ag(NO _{3}) _{2} \rightarrow Cu(NO _{3}) _{2} + Ag$

Multiple choice chemistry aldehydes, ketones and carboxylic acids alkanoic acids nomenclature of carboxyl group nomenclature of carboxylic acids

Sodium salt of an organic acid 'X' produces effervescence with conc. $H _2SO _{4}$. 'X' reacts with the acidified aqueous $CaCl _2$ solution to give a white precipitate which decolourises acidic solution of $KMnO _4$. 'X' is 

  1. $C _6H _5COONa$
  2. $HCOONa$
  3. $CH _3COONa$
  4. $Na _2C _2O _4$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sodium oxalate (Na2C2O4) reacts with H2SO4 to release CO/CO2, and with CaCl2 to form calcium oxalate (white precipitate). Calcium oxalate is then oxidized by KMnO4 in acidic medium.