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) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

Alkali metals readily react with oxyacids forming corresponding salts like ${ M } _{ 2 }{ CO } _{ 3 }$, ${ M }H{ CO } _{ 3 }$, ${ M }N{ O } _{ 3 }$, ${ M } _{ 2 }{ SO } _{ 4 }$, etc. with evolution of hydrogen. They also dissolve in liquid ${ NH } _{ 3 }$ but without the evolution of hydrogen. The color of its dilute solution is blue but when it is heated and concentrated then its color becomes bronze.

Which of the following statement about the sulphate of alkali metal is correct :

  1. except ${ Li } _{ 2 }{ SO } _{ 4 }$ all sulphate of other alkali metals are soluble in water.

  2. all sulphates of alkali metals except lithium sulphate forms alum.

  3. the sulphates of alkali metals cannot be hydrolysed.

  4. all of these.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Except ${ Li } _{ 2 }{ SO } _{ 4 }$ all sulphate of other alkali metals are soluble in water and forms alum. Thus, they form double salts with the sulphates of trivalent metals like $Al, Fe, Cr$ etc. The sulphates of alkali metals cannot be hydrolysed as they are salts of a strong acid and strong base. 
Multiple choice chemistry change around us physical changes changes and their classification physical changes

You mix two colorless solutions and the resulting mixture becomes cloudy. What type of reaction was observed?

  1. A physical reaction

  2. A redox reaction

  3. A precipitation reaction

  4. An acid base reactions.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When two colourless solutions react to form a cloudy precipitate which settles at bottom of a solution then the reaction is said to be precipitation reaction.

Ex :- ${ AgNO } _{ 3 }+NaCl\rightarrow AgCl+{ NaNO } _{ 3 }$

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

A small piece of silver is placed in a solution containing both magnesium nitrate and copper (II) nitrate. Which one of the following occurs?

  1. No reaction takes place

  2. The silver dissolves and only copper is precipitated

  3. The silver dissolved and only magnesium is precipitated

  4. A mixture of magnesium and copper forms on the silver
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Silver is the metal which is present at the bottom of reactivity series below $Mg$ and $Cu$ metals so it cannot displace these metals from its solution. In this case, no reaction takes place by this piece of silver.

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

Metal $A + \ $ Salt solution of $B\rightarrow $ Salt solution of  $A + \ $ Metal $B$
Which one is more reactive among $A$ and $B$?

  1. $A$
  2. $B$

  3. Both are equally reactive

  4. None of the baove
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Metal $A$ displaces metal $B$ from its solution. Hence, it is more reactive than $B$.

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

In a solution of lead acetate, a strip of metal Z was dipped. After some time, lead from the solution was deposited at the metal strip. Which is more reactive?

  1. $Z$

  2. Lead

  3. Both have equal reactivity

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$Z$ is more reactive. It replaced lead from its compound.

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

An unidentifed metal ($X$) gives the following data in an activity series experiment.
$X(s)+Cr{Cl} _{2}(aq)$- color change and bubbles are produced.
$Sr(s)+XCl(aq)$- no change.
Where should element "$X$" be placed on the activity series?

  1. Above $Sr$
  2. Above both $Cr$ and $Sr$
  3. Above $Cr$ below $Sr$
  4. Below $Cr$ above $Sr$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In first reaction, $X(s)+CrCl _2(aq)\longrightarrow \text{ color change }+\text{ Bubbles formed.}$

The reaction occur here, So, $X$ is more reactive than $Cr.$
In second reaction, $Sr+XCl\longrightarrow \text{ No change.}$
This reaction is not possible, because $Sr$ is less reactive than $X.$
So, in both cases, $X$ is more reactive. 
So, $X$ should be placed above $Cr$ and $Sr$ in activity series.

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

Zinc sulphate forms a colourless solution in water. Colour on adding copper  is :

  1. blue

  2. black

  3. brown

  4. no change in colour
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

There will be no change in colour as copper(Cu) is less reactive metal than zinc(Zn) and thus cannot displace the latter from $ZnSO _{4}$ solution.

Multiple choice botany transpiration guttation excretion in plants long distance transport of water

The whitish powder around hydathode is due to 

  1. Guttation

  2. Salt depositon from air

  3. Salt formation over surface

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

Loss of water as dilute solution of minerals and salts from hydathodes is called as guttation. It is prominently seen when transpiration is low but root pressure is high. When water evaporates, the mineral salts are left behind as whitish deposits.

Therefore, the correct answer is option A.

Multiple choice chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

Aqueous solution of which of the following salts turns the red litmus blue?

  1. $Na _2CO _3$
  2. $NaHCO _3$
  3. $Na _2CO _3\cdot 10H _2O$

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

Sodium carbonate and sodium bicarbonate are basic salts which turn red litmus blue as they are alkaline in nature having pH more than 7.

Multiple choice chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

Which of the following are efflorescent substances?

  1. $Cu{SO} _{4}.5{H} _{2}O$
  2. ${Na} _{2}{CO} _{3}.10{H} _{2}O$
  3. ${K} _{2}{SO} _{4}.{Al} _{2}{({SO} _{4})} _{3}.24{H} _{2}O$
  4. ${({NH} _{4})} _{2}{SO} _{4}$
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

An efflorescent substance is a chemical which has water associated with its molecules, and which, when exposed to air, loses this water through evaporation. An example of an efflorescent substance is the common copper(II) sulfate crystal $(CuSO _4.5H _2O)$, a blue crystalline solid that when exposed to air, slowly loses water of crystallization from its surface to crystallize to form a white layer of anhydrous copper(II) sulfate.


$Na _2CO _3.10H _2O$ loses 9 water molecules first and then becomes completely anhydrous. 

${K} _{2}{SO} _{4}.{Al} _{2}{({SO} _{4})} _{3}.24{H} _{2}O$ is not an efflorescent as its crystals do not lose water of crystallization by efflorescence nor it is oxidised in the air. ${({NH} _{4})} _{2}{SO} _{4}$ do not has associated water molecules.

Multiple choice chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

A sodium salt on treatment with ${MgCl} _{2}$ gives white precipitate only on heating. The anion of the sodium salt is:

  1. $ { HCO } _{ 3 }^{ - }$
  2. $ { CO } _{ 3 }^{ 2- }$
  3. $ { NO } _{ 3 }^{ - }$
  4. $ { SO} _{ 4 }^{ 2- }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The salt will be sodium bicarbonate and the anion is $HC{ O } _{ 3 }^{ \ominus  }$
When sodium bicarbonate react with $Mg{ Cl } _{ 2 }$ it produce Magnesium bicarbonate which is also soluble in water
But, on heating $Mg{ \left( HC{ O } _{ 3 } \right)  } _{ 2 }$ it produce $Mg\left( C{ O } _{ 3 } \right) $ which gives white precipitate
$Mg{ \left( HC{ O } _{ 3 } \right)  } _{ 2 }\rightarrow Mg\left( C{ O } _{ 3 } \right)+C{ O } _{ 2 }+{ H } _{ 2 }O$
Multiple choice chemistry properties of natural resources conservation of water and recycling properties of water structure and properties of water

During hydrate formation from aqueous solution water can be associated in different forms. Indicate the wrong combination. 
Coordinated water -$[Cr(H _{2}O) _{6}]^{3+}3Cl^{-}$
Interstitial water - $BaCl _{2}.2H _{2}O$
Hydrogen bonded water --$[Cu(H _{2}O) _{4}]^{2+}SO _{4}^{2-}.H _{2}O$

  1. (i)

  2. (ii)

  3. (iii)

  4. none of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Coordinated water is water that is a ligand in a metal complex. The metal atom and the water molecules are held together by coordinate bonds.
Interstitial water is water that is present in the interstitial sites of a crystal lattice.
Hydrogen-bonded water is the water that that is linked to some other ion by hydrogen bonding.
Multiple choice chemistry general principles of metallurgy extraction of copper and zinc extraction of copper and zinc from their oxides basics of metallurgy

Which of the following two substances react to produce blister copper?

  1. $Cu _{2}S _{(s)}$ and $Cu _{2}O _{(s)}$
  2. $Cu _{2}O _{(s)}$ and $FeS _{(s)}$
  3. $Cu _{2}S _{(s)}$ and $O _{2(g)}$
  4. $Cu _{2}S _{(s)}$ and $FeS _{2(s)}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Blast of air converts $Cu _2S$ partly into $Cu _2O$ which reacts with remaining $Cu _2S$ to give molten copper. The copper so obtained is called "Blister copper" because, as it solidifies, $SO _2$ hidden in it escapes out producing blister on its surface

option A is correct

Multiple choice enzymes and catalysts catalysis adsorption and colloids surface chemistry chemistry adsorption theory of heterogeneous catalysis

Presence of traces of arsenious oxide ($As _{2}O _{3}$) in the reacting gases $SO _{2}$ and $O _{2}$ in presence of platinised asbestos in contact process acts as:

  1. catalytic promoter

  2. catalytic poison

  3. dehydrating agent

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

  • Promoters are substances that enhance the activity of a catalyst while poisons decrease the activity of a catalyst.
  • In the manufacturing of sulfuric acid, a step involves the reaction of $SO _2$ and $O _2$ in presence of platinized asbestos to give $SO _3$
                    .i.e. $SO _2+O _2 \rightarrow SO _3$ 
In the above reaction if traces of arsenious oxide ($As _2O _3$)  is used then it acts as the catalytic poison by reducing the catalytic activity of Platinised asbestos.