Tag: chemistry

Questions Related to chemistry

The function of quick lime mixture is to:

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

  1. Absorb moisture present in soda lime

  2. increase the efficiency of soda lime

  3. Increase the pH of soda lime

  4. Take part in reaction with NaOH

Show answer
Correct Option: A
Explanation:

$CaO$ is a compound that absorbs moisture easily and rapidly.

So it is used in some lime. It also adsorbs $CO _2$
Hence option A is the correct answer.

What is the correct order of thermal stability of carbonates of alkaline earth metals?

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

  1. $BeCO _3 > MgCO _3 > CaCO _3 > SrCO _3 > BaCO _3$

  2. $BeCO _3 < MgCO _3 < CaCO _3 < SrCO _3 < BaCO _3$

  3. $BeCO _3 < MgCO _3 > CaCO _3 > SrCO _3 < BaCO _3$

  4. $BeCO _3 > MgCO _3 < CaCO _3 < SrCO _3 < BaCO _3$

Show answer
Correct Option: B
Explanation:

Correct order of thermal stability of carbonates of alkaline earth metals is
$BeCO _3 < MgCO _3 < CaCO _3 < SrCO _3 < BaCO _3$

Setting of plaster of paris involves:

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

  1. oxidation with atmospheric oxygen

  2. combination with atmospheric $CO _{2}$

  3. dehydration

  4. hydration to yield another hydrate

Show answer
Correct Option: D
Explanation:

On hydration of Plaster of Paris, converts into Gypsum.
$\underset {\text {Plaster of Paris}}{CaSO _{4} \cdot \dfrac {1}{2} H _{2}O} + \dfrac {3}{2} H _{2}O\rightarrow \underset {Gypsum}{CaSO _{4}\cdot 2H _{2}O}$

The uses of plaster of paris are:

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

  1. it is used as plaster for supporting fractured bones

  2. for making toys and material for decoration

  3. for making smooth surface

  4. all of the above

Show answer
Correct Option: D
Explanation:

Some of the uses ofplaster of paris are as follows :-

1. It is used in medicine to make plaster casts to immobilize broken bones and hence used for supporting fractured bones.
2. It is also used to make and hold parts of ornamental plasterwork on ceilings. Thus, it is used in decoration and for making toys.
3.It can be also used to make surfaces smooth.
Hence, the correct answer is option (D).

Identify which contributes for strengthening of lime mortar structures and contributes for weakening of RCC structures the factor(s).

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

  1. Usage of water containing dissolved salts

  2. Addition of lime

  3. Absorption of $CO _2$ from atmospheric air

  4. Both B and C

Show answer
Correct Option: C
Explanation:

Absorption of $CO _{2}$ from atmospheric air contributes for strengthening for lime mortar structure as when atmospheric $CO _{2}$ combines with hydrated lime, limestone is formed which is a solid.

RCC structures are plain cement concrete reinforced with steel bars. Generally, the pH of new concrete is 12-13 which surrounds embedded reinforcement with the passivating layer of highly alkaline cement protecting reinforcement against corrosion. When atmospheric $CO _{2}$ comes in contact with the RCC structure it gets corroded and production of $CaCO _{3}$ occurs due to which alkalinity of the concrete decreases and the steel reinforcement is then susceptible to corrosion. This is how RCC structure gets weaken in the presence of atmospheric $CO _{2}$

Cement is manufactured from:

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

  1. clay

  2. limestone

  3. sodium chloride

  4. both A and B

Show answer
Correct Option: D
Explanation:

Two of the raw materials for the manufacture of cement are limestone and clay.


Hence, the right answer is both (A) and (B).

Raw materials used for the manufacture of Portland cement are:

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

  1. gypsum and limestone

  2. limestone and clay

  3. alumina, clay and gypsum

  4. gypsum and clay

Show answer
Correct Option: B
Explanation:

Limestone and clay are raw materials used in the manufacture of portland cement.

Chemical formula of epsom salt is $CaSO _4.2H _2O$

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

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

Magnesium salt is also known as epsom salt. Chemical formula of epsom salt is $MgSO _4.7H _2O$.

A mixture of slaked lime, sand and water is known as ______.

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

  1. portland cement

  2. lime mortar

  3. milk of lime

  4. alabaster

Show answer
Correct Option: A
Explanation:

Portland cement contains calcium oxide (quicklime) and clay (silica along with small quantity of alumina, magnesia and ferric oxide).

Plaster of paris hardens by :

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

  1. giving $CO _{2}$

  2. changing into carbonate

  3. uniting with water

  4. giving out water

Show answer
Correct Option: C
Explanation:
$\underset{\text{plaster of paris}}{CaSO _4.1/2H _2O} \xrightarrow[\text{setting}]{H _2O} \underset{\begin{matrix}\text{gypsum}\\\text{othorhombic}\\\text{dihydrate}\end{matrix}}{CaSO _4.2H _2O} \xleftarrow[\text{hardening}]{} \underset{\begin{matrix} \text{gypsum} \\\text{monoclinic dihydrate}\end{matrix}}{CaSO _4.2H _2O}$

Plaster of paris absorbs water to form dihydrate, which sets to form a hard unified mass.