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

The molecular formula is a short form representation of

  1. A compound

  2. An element

  3. A mixture

  4. An alloy
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

 A chemical formula that shows the total number and kinds of atoms in a molecule, but not their structural arrangement or the molecular formula is a short form representation of a compound.

Multiple choice law of reciprocal proportion laws of chemical combination basic concepts of chemistry some basic concepts of chemistry chemistry

The weight ratio of two elements A and B which combine with the fixed weight of C separately is either the same or some simple whole number multiple of the weight ratio in which A and B combine together. This statement explains :

  1. law of multiple proportion.

  2. law of reciprocal proportion.

  3. law of conservation of mass.

  4. law of constant composition.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The weight ratio of two elements A and B which combine with the fixed weight of C separately is either the same or some simple whole number multiple of the weight ratio in which A and B combine together. This statement explains the Law of reciprocal proportion.
For example, 23 g of $Na$ combines with 35.5 g of $Cl$ and 1 g of $H$ to form $NaCl$ and $NaH$. Hence, 35.5 g of $Cl$ and 1 g of $H$ will combine to form $HCl$.

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

Nitrolim is a mixture of :

  1. $CaC _2$ and graphite
  2. $CaCN _2$ and graphite
  3. $Ca(CN) _2$ and graphite
  4. $CaCN _2+N _2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
 $CaC _2 +N _2\longrightarrow CaCN _2 +C$

When nitrogen is passed over calcium carbide at a suitable high temperature, we get a mixture of $CaCN _2 + Graphite (C)$ known as nitrolim which is a nitrogenous fertiliser." 

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.

Multiple choice polyhalogen compounds haloalkanes and haloarenes chemistry

What is not a polyhalogen?

  1. Methyl chloride

  2. Dichloro methane

  3. Chloroform

  4. Carbon tetrachloride
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A polyhalogen compound contains more than one halogen atom in its molecule. Methyl chloride (CH3Cl) contains only one chlorine atom, making it a monohalogen compound, not a polyhalogen.

Multiple choice chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

Argyrol is a:

  1. Ferric oxide sol

  2. Silver sol

  3. Gold sol

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

Argyrol is a silver sol and is used as an eye lotion.It is manufactured in the chemical industry to pharmaceutical grade only, using denatured pharmaceutical-grade protein for ophthalmic application and elemental silver, to produce the silver protein molecule.