Chemistry · Science General

Common Chemical Compounds and Reactions

1,197 Questions

Common chemical compounds and reactions questions test your knowledge of everyday chemicals, their formulas, and their interactions. Topics include properties of acids and bases, hard water chemistry, and compounds like baking soda and plaster of paris. This section is essential for general science preparation.

Acids and basesPlaster of parisHard water chemistryCommon chemical formulasEveryday chemical reactions

Common Chemical Compounds and Reactions Questions

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

Gypsum is added to cement in order to:

  1. prolong hydration

  2. increase strength after hydration

  3. decrease heat of hydration

  4. reduce curing time
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Gypsum is called the retarding agent of cement which is mainly used for regulating the setting time of cement and is an indispensable component. Without gypsum, cement clinker can condense immediately by mixing with water and release heat. The major reason is that C3A in the clinker can dissolve in water quickly to generate a kind of calcium aluminate hydrate, a clotting agent, which will destroy the normal use of cement. The retardation mechanism of gypsum is: when cement is hydrated, gypsum reacts with C3A quickly to generate calcium sulfoaluminate hydrate which deposits and forms a protection film on the cement particles to hinder the hydration of C3A and delay the setting time of cement.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

The process of formation of colloidal gel from calcium silicate and aluminates is:

  1. endothermic

  2. exothermic

  3. reversible
  4. both $B$ and $C$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The first stage of hydration is characterized by the rapid dissolution of clinker

${ Ca } _{ 3 }Si{ O } _{ 5 }+3{ H } _{ 2 }O\longrightarrow 3{ Ca }^{ 2+ }+4{ OH }^{ - }+{ H } _{ 2 }Si{ O } _{ 2 }^{ 4- }$

 immediately after the wetting of the clinker powder. In calorimetry measurements,  a large exothermic signal is measured due to wetting and dissolution of clinker. The wet clinker releases ions such as calcium, silicate and hydroxide to the solution. From the evolution of these ion concentrations the dissolution rate of clinker can be evaluated.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

Portland cement consists essentially of compounds of:

  1. lime (calcium oxide, $CaO$)
  2. silica (silicon dioxide, $SiO _2$)
  3. alumina (aluminum oxide, $Al _2O _3$)

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

Limestone, sand, gypsum and coal dust are the materials required for the manufacture of cement. Lime, silica and alumina are contained in the above materials. Hence, the right answer is all of them.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

Metal oxide that turns into cement upon roasting with clay is:

  1. $NO$
  2. $MgO$
  3. $BaO$
  4. $CaO$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Quicklime when roasted with clay forms cement. Calcium oxide is also called as quicklime. Hence, the metal oxide that forms clay on roasting with clay is $CaO$.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

Which of the following is not present in portland cement?

  1. $Ca _3Al _2O _6$
  2. $Ca _3SiO _5$
  3. $Ca _2SiO _4$
  4. $Ca _3(PO _4) _2$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • Portland cement gets its strength from chemical reactions between the cement and water. The process is known as hydration.
  • Chemical composition of portland cements are-
  1.  $Ca _3Al _2O _6$
  2. $Ca _3SiO _5$
  3. $Ca _2SiO _4$
  4. $Na _2O$
  5. $K _2O$
  6. $CaSO _4.2H _2O$
  7. $Ca _4Al _2Fe _2O _{10}$
  • Hence option D is not present in portland cement.
Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

When plaster of paris comes in contact with water it sets into a hard mass. The composition of the hard mass is:

  1. $CaSO _4.H _2O$
  2. $CaSO _4.Ca(OH) _2$
  3. $CaSO _4.2H _2O$
  4. $CaSO _4.2Ca(OH) _2$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When plaster of paris comes in contact with water it sets into a hard mass which is called gypsum. Its composition is $CaSO _4.2H _2O$

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

Gypsum is added to Portland cement to:

  1. fasten the process of setting

  2. slow down the process of setting

  3. improve the colour of the cement

  4. increase the melting point of cement
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Gypsum slows down the process of setting of the cement so that it gets sufficiently hardened.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

Cement, the important building material is a mixture of oxides of several elements. Besides calcium, iron and sulphur, oxides of elements of which of the group (s) are present in the mixture?

  1. Group 2

  2. Groups 2, 13 and 14

  3. Groups 2 and 13

  4. Groups 2 and 14
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Cement is a mixture of calcium (present in group 2) and aluminium silicates (contains group 13 and 14 elements).
Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

Cement is a mixture of:

  1. calcium silicates

  2. calcium aluminates

  3. calcium silicates and aluminates

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cement is an important building material. It is also called Portland cement. Important ingredients of Portland cement are dicalcium silicate $\left( { Ca } _{ 2 }{ SiO } _{ 4 } \right) 26$%, tricalcium silicate $\left( { Ca } _{ 3 }{ SiO } _{ 5 } \right) 51$% and tricalcium aluminate$\left( { Ca } _{ 3 }{ Al } _{ 2 }{ O } _{ 6 } \right) 11$%.


Hence, cement is a mixture of calcium silicates and aluminates.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) some important compounds of calcium some important compounds of magnesium and calcium compounds of s block elements

Gypsum is added to clinker during cement manufacturing to:

  1. Decrease the rate of setting of cement

  2. Bind the particles of calcium silicate

  3. Facilitate the formation of colloidal gel

  4. All of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

During the cement manufacturing process, upon the cooling of the clinker, a small amount of gypsum is introduced during the final grinding process. Gypsum is added to control the setting of cement. 


If not added, the cement will set immediately after mixing water leaving no time for concrete placing. Hence, the addition of gypsum is required to decrease the rate of setting.


Hence, option $(A)$ is correct.

Multiple choice chemistry nitrogen and sulfur nitrogen gas component of air - nitrogen nitrogen

Which of the following compound has nitrogen percentage highest?

  1. Ammonium nitrate

  2. Ammonium sulphate

  3. Calcium cyanamide

  4. Urea
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Urea (CO(NH2)2) has a molecular weight of 60 g/mol and contains two nitrogen atoms, providing a nitrogen mass percentage of about 46.6 percent, which is higher than ammonium nitrate, ammonium sulphate, or calcium cyanamide.

Multiple choice chemistry separation of matter sedimentation, decantation and filtration other methods of separation separation methods

Water is said to be permanently hard when it contains:

  1. chloride and sulphates of Mg and Ca

  2. bicarbonate of Na and K

  3. carbonate of Na and K

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Permanent hardness in water is caused by the presence of dissolved chlorides and sulfates of calcium and magnesium, which cannot be removed by boiling.

Multiple choice chemistry separation of matter sedimentation, decantation and filtration other methods of separation separation methods

When a mixture of common salt and ammonium chloride is heated, white fumes are liberated which change into a white deposit when cooked. What is this substance?

  1. Ammonium chloride

  2. Common salt (sodium chloride)

  3. A mixture of ammonium chloride and common salt

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

On heating the mixture of common salt and ammonium chloride in a china dish white fumes evolve and rise inside the funnel the china dish and cover it, to collect the fumes of the sublimating substance.

We collect fumes of ammonium chloride not of common salt because ammonium chloride is a sublimating substance and common salt is not a sublimating substance.

Multiple choice chemistry separation of matter sedimentation, decantation and filtration other methods of separation separation methods

Compounds evaporating easily and giving off a smell are:

  1. ionic compounds.

  2. covalent bonds.

  3. metallic bonds.

  4. diatic bonds.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Odour is the result of the compound vaporising, or at least being a gas, so that your olfactory system is capable of detecting it. If a compound is not so volatile that it vaporises at room temperature, it will not give off an odour.Compounds like methane, benzene etc. that possess covalent bonds are volatile at room temperature hence, gives off smell.