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 the s-block elements (alkali and alkaline earth metals) uses of alkali and alkaline earth metals uses of s block elements group 1 elements: alkali metals

A metal salt solution forms a yellow precipitate with potassium chromate in acetic acid, a white precipitate with dilute sulphuric acid but does not give precipitate with sodium chloride or iodide. The white precipitate obtained when sodium carbonate is added to the metal salt solution will consist of:

  1. lead carbonate

  2. basic lead carbonate

  3. barium carbonate

  4. strontium carbonate
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pb and Ba both give yellow ppt with $K _2CrO _4$ in acetic and white precipitate with dil. $H _2SO _4$. but lead salts give a precipitate with sodium chloride or iodide also whereas barium does not. It means given salt is barium salts and with sodium carbonate, it gives a white precipitate of barium carbonate.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) uses of alkali and alkaline earth metals uses of s block elements group 1 elements: alkali metals

Beautiful colours of fireworks are produced by adding salts of various metals into the burning mixture. The firework colours of different metals are mentioned here. Pick the false one.

  1. Calcium gives a brick-red light

  2. Sodium gives a yellow light

  3. Copper gives a green light

  4. Strontium gives a blue light
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
The Magical Colors of Fireworks
  • Red-strontium salts, lithium salts.
  • Orange- calcium salts.
  • Gold-incandescence of iron (with carbon), charcoal, or lampblack.
  • Yellow-sodium compounds.
  • White-white-hot metal, such as magnesium or aluminum.
  • Green-barium compounds + chlorine producer,copper.
  • Blue-copper compounds + chlorine producer.
  • Brick-red light-Calcium

Hence option D is wrong option.
Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) uses of alkali and alkaline earth metals uses of s block elements group 1 elements: alkali metals

Sparkling red colour after the blast of fire crackers is due to the presence of:

  1. sulphur

  2. sodium

  3. strontium

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

Firework colors come from the use of metal salts, packed in pellets called “stars.”Metal salts commonly used in firework displays include: strontium carbonate (red fireworks), calcium chloride (orange fireworks), sodium nitrate (yellow fireworks), barium chloride (green fireworks) and copper chloride (blue fireworks). 

Hence,Sparkling red colour after the blast of fire crackers is due to the presence of Strontium.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) biological importance of sodium and potassium biological importance of elements biological importance of s block elements biological importance of magnesium and calcium

Select the correct statement with respect to sodium peroxide?

  1. It decolourises the $KMnO _4$ solution.
  2. On heating with oxygen at $450^0C$ and 300 atm pressure, it becomes paramagnetic.
  3. It is obtained along with sodium metal when sodium oxide is heated to a temperature more than $400^oC$.

  4. It gives both hydrogen peroxide and oxygen gas with water as well as with sulphuric acid.
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

(A) $2Mn{ O } _4^-(pink)+16H^++5O _2^{2-}\rightarrow 2Mn^{2+}+8H _2O+5O _2$.
(B) $Na _2O _2+O _2\xrightarrow [300 atm]{> 450^oC} 2NaO _2 ({ O } _2^-$ contains on unpaired electron in $\pi^*$ MO).
(C) $2Na _2O\xrightarrow {400^oC} Na _2O _2+2Na$.
(D) Gives only $H _2O _2$.

Multiple choice limestone uses of group 2 compounds group 2 industrial inorganic chemistry chemistry

Following compounds are used in fire-works :

  1. $LiNO _{3}$
  2. $BaCl _{2}$
  3. $(NH _{4}) _{2}Cr _{2}O _{7}$

  4. all of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All compounds are used in fire works.
$LiNO _{3}$ on ignition imparts crimson red,
                        $BaCl _{2} \rightarrow $ green
           $(NH _{4}) _{2}Cr _{2}O _{7}\rightarrow$ green.

Multiple choice chemistry chemical equilibrium equilibrium in physical processes introduction to equilibrium chemical equilibrium and acids-bases

A yellow precipitate obatined in II group of the equilibrium analysis was soluble in aq. $NaOH$ and insoluble in dil. $HNO _3$. This shows the presence of:

  1. $Tin$
  2. $Antimony$
  3. $Arsenic$
  4. $Cadmium$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In qualitative analysis, Tin (Sn) sulfides (SnS2) are soluble in yellow ammonium sulfide or NaOH, forming a soluble complex, and precipitate upon acidification with dil. HNO3 or HCl.

Multiple choice distinction between pairs of amines organic compounds containing nitrogen organic compounds with functional group containing nitrogen chemistry

A colourless liquid $A(b.p:184^\circ:C)$ is sparingly soluble in warm water to which it gives feebly alkaline reaction on treating with $NaNO _{2}:and:dil:HCl$ in the cold solution, it yields a solution which reacts with an alkaline solution of $\beta-$napthol to give an orange yellow precipitate. Compound $A$ is :

  1. $C _{6}H _{5}N _{2}Cl$
  2. $C _{6}H _{5}NHNH _{2}$
  3. $n-C _{4}H _{9}NH _{2}$
  4. $C _{6}H _{5}NH _{2}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Aniline is the colourless liquid A having boiling point $184 ^oC$.
On treatment with $NaNO _{2}:and:dil:HCl$ at low temperature, it forms benzne diazonum salt.
The diazonium salt reacts with napthol in alkaline medium to form azo dye which is n orange yellow precipitate.

Multiple choice chemistry atoms, molecules and radicals molecular formula and valency valency and chemical formulae combining capacity and chemical formulae

The formula of iron (III) sulphate is:

  1. $Fe _3CO _4$
  2. $Fe _2(SO _4) _3$
  3. $Fe _2(CO _4) _3$
  4. $FeCO _4$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

It is given that the valency of iron in iron sulphate is $+3$ and we know that for sulphate $({SO _4}^{2-})$, it is $-2$. Therefore, the formula is $Fe _2(SO _4) _3$.


$2Fe^{+3} +3{SO _4}^{-2} \rightarrow Fe _2(SO _4) _3$
                                  Iron (III) sulphate

Hence, option B is correct.

Multiple choice chemistry the language of chemistry percent composition percentage composition and empirical formula empirical formula, percentage composition and molecular formula water of crystallisation

What changes does not occur in presence of organic solvent when acidified $K _{2}Cr _{2}O _{7}$ reacts with $H _{2}O _{2}$ solutions

  1. Orange colour of solution turns blue
  2. $O.S$ if $Cr$ atom decreases
  3. $O.S$ of $Cr$ atom remains constant

  4. Unpaired electron remain same
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice chemistry substances in common use salts and their properties study of some important salts salts used in daily life

Sodium chloride imparts a yellow color to the Bunsen flame. This can be interpreted due to the :

  1. low ionisation of energy of sodium

  2. sublimation of metalic sodium to give yellow vapour

  3. emission of excess energy absorbed as a radiation in the visible region

  4. photo sensitivity of sodium
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Sodium chloride imparts a yellow color to the Bunsen flame. This can be interpreted due to the emission of excess energy absorbed as a radiation in the visible region.
When an alkali or akaline earth metal (or its salt) is introduced in the flame, the valence electrons of the metal absorbs energy and are excited to the higher energy level. When excited electrons return to their ground state, they release the absorbed energy as visible light.
Multiple choice bio-chemistry biological oxidation classical idea of redox reactions oxidation reduction redox reaction

When a piece of magnesium ribbon is placed in a beaker of copper sulfate solution, which one of the following is most likely to happen?

  1. A vigorous reaction immediately takes place, with the release of a lot of heat.

  2. The blue colour of the copper sulfate solution gets darker.

  3. The blue colour of the copper sulfate solution gets lighter.

  4. The magnesium catches fire.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$Mg+CuSO _4 \longrightarrow MgSO _4 + Cu$

            $(Blue)$
By adding$Magnesium$ to $CuSO _4$, it turns to $MgSO _4.$
Because $Mg$ is above $Cu$ in reactivity series. So $Mg$ displaces $Cu$ in $CuSO _4$. As reaction processes, $CuSO _4$ content decreases.
$\therefore$ Color blue fades. 

Multiple choice hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry

Which of the following would seperate $\displaystyle { H } _{ 2 }{ S }$ at pH < 7 ?

  1. $\displaystyle { Zn }^{ 2+ },{ Co }^{ 2+ }$
  2. $\displaystyle { Cu }^{ 2+ },{ Cd }^{ 2+ }$
  3. $\displaystyle { Cu }^{ 2+ },{ Cr }^{ 3+ }$
  4. $\displaystyle { Cu }^{ 2+ },{ As }^{ 3+ }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\displaystyle { H } _{ 2 }{ S }$ would separate $\displaystyle { Cu }^{ 2+ },{ Cr }^{ 3+ }$ at pH<7 .
$Cu^{2+} +  H _2S \uparrow \rightarrow  \underset {black  ppt} {CuS} + 2H^+$

Multiple choice hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry
Unknown metal Appearance Reactions with dilute HCl Reaction with dilute HNO$ _3$
  (1) Dull gray solid with white oxide coating  Dissolved with bubbles of clear gas  Dissolved with bubbles of clear gas
  (2) Solid, lustrous smooth silver-gray surface No reaction  Dissolved with bubbles of orange gas

Which of the following represents unknown metal (1)  ?

  1. Mercury

  2. Copper

  3. Zinc

  4. Iron

  5. Silver
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Unknown metal (1) could be zinc as it is dull gray solid with white oxide coating.
Note: Mercury is a liquid, copper is brownish, iron has orange brown coating of oxide (rust) and silver has gray-black colour.

Multiple choice hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry
Unknown metal Appearance Reactions with dilute HCl Reaction with dilute HNO$ _3$
  (1) Dull gray solid with white oxide coating  Dissolved with bubbles of clear gas  Dissolved with bubbles of clear gas
  (2) Solid; lustrous smooth silver-gray surface No reaction  Dissolved with bubbles of orange gas

Which of the following represents unknown metal (2) ?

  1. Carbon

  2. Copper

  3. Zinc

  4. Sodium

  5. Silver
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Unknown metal (2) could be silver. It is a relatively inert metal. 
Note: Carbon is not a metal. Copper is brownish, zinc is reactive metal with whitish oxide coat in air. Sodium is highly reactive and explodes when it comes in contact with water. It reacts with acids even violently.

Multiple choice hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry
Unknown metal Appearance Reactions with dilute HCl Reaction with dilute HNO$ _3$
  (1) Dull gray solid with white oxide coating  Dissolved with bubbles of clear gas  Dissolved with bubbles of clear gas
  (2) Solid; lustrous smooth silver-gray surface No reaction  Dissolved with bubbles of orange gas

The transparent gas is produced by the addition of dilute HCI to unknown metal (1). Which of the following represents the transparent gas ?  

  1. Cl$ _2$
  2. H$ _2$
  3. O$ _2$
  4. CO$ _2$
  5. NO$ _2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When dilute $HCl$ is added to the unknown metal  (1) (zinc), the transparent gas produced is hydrogen. 
Note: Chlorine and $NO _2$ gases are green and orange coloured respectively. $CO _2$ is not possible as no $C$ atoms are present.
Also, metals react with acids to form hydrogen gas.