Tag: some important compounds of magnesium and calcium

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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 reaction of water with slaked lime is studied by ________ .

  1. putting slaked lime into water taken in a test tube

  2. putting a lot of water into slaked lime.

  3. sprinkling a little water on slaked lime.

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

The reaction of water with calcium oxide (quicklime) to form slaked lime is highly exothermic. To study it safely, one typically adds small amounts of water to the lime or vice-versa under controlled conditions, but the standard laboratory demonstration involves adding water to the solid.

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

$A \, Ca(HCO _3) _2 + B \, Ca(OH) _2 \to C \, CaCO _3 + D \, H _2O$. 


Choose the correct option.

  1. $A = 1$
  2. $B = 1$
  3. $C = 1$
  4. $D = 2$
Reveal answer Fill a bubble to check yourself
A,B,D Correct answer
Explanation

$ACa(HCO _3) _2 + BCa(OH) _2 \rightarrow CCaCO _3 + DH _2O$

First, balance calcium then oxygen ,then hydrogen.

$Ca(HCO _3) _2 + Ca(OH) _2 \rightarrow 2CaCO _3 + 2H _2O$
                       (This the balanced equation)

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 function of quick lime mixture is to:

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  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. $BeCO _3 > MgCO _3 < CaCO _3 < SrCO _3 < BaCO _3$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

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

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

Setting of plaster of paris involves:

  1. oxidation with atmospheric oxygen
  2. combination with atmospheric $CO _{2}$

  3. dehydration

  4. hydration to yield another hydrate
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

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

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 uses of plaster of paris are:

  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
Reveal answer Fill a bubble to check yourself
D Correct answer
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).

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

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

  1. Usage of water containing dissolved salts

  2. Addition of lime
  3. Absorption of $CO _2$ from atmospheric air

  4. Both B and C
Reveal answer Fill a bubble to check yourself
C Correct answer
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 $CO _{2}$