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Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Which of the following element has $2^{nd} IP<1^{st}IP$?

  1. $Mg$
  2. $Na$
  3. $C$

  4. None
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All three $Mg$, $C$ and $Ne$ have $2nd$ ionisation potential greater than $1st$ ionisation potential. 

This is the general trend shown by most element that $1^{st} IP<2^{nd} IP<3^{rd} IP<$ and so on.
Hence, option D is correct.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Gypsum is a widely occurring mineral. It is the sulphate of calcium with two molecules of water attached. On heating it loses three-quarters of its water and becomes:

  1. baking soda

  2. plaster of Paris

  3. a pearl

  4. an ultramarine
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
It is prepared by heating Gypsum to a temperature of 373K. When gypsum is heated to a temperature of 373K, it loses three-fourths of its water of crystallization and forms Plaster of Paris.
$\underset{\text{Gypsum}}{CaS{O} _{4}.2{H} _{2}O} \xrightarrow[373 K]{\Delta} \underset{\text{Plaster of Paris}}{CaS{O} _{4}.\cfrac{1}{2}{H} _{2}O} + \cfrac{3}{2}{H} _{2}O$
Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Gypsum is added to cement clinker to:

  1. decrease the rate of setting of cement

  2. bind the particles of calcium silicate

  3. increase the tensile strength of the cement

  4. facilitate the formation of colloidal gel
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Gypsum plays a very important role in controlling the rate of hardening of the cement. It slows sown the setting of cement so that cement is adequately hardened.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Calcium sulphate is found in nature in two forms, anhydrous calcium sulphate and hydrated calcium sulphate is heated with coke, sulphur dioxide gas is obtained. When hydrated calcium sulphate is heated at $200^oC$, it forms anhydrous salt.

When calcium sulphate is mixed with conc. $HCl$ and the paste is formed. What colour is obtained when a pinch of this paste is brought near the flame?

  1. golden yellow

  2. brick red

  3. crimson red

  4. apple green
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When calcium sulphate is mixed with conc. HCl the paste is formed. When this paste is brought near the flame, brick red colour is obtained which is the characteristic colour of calcium.


Golden yellow is the characteristic colour of sodium.

Crimnson red is the characteristic colour of strontium.

Apple green is the characteristic colour of barium.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Silica reacts with magnesium to form a magnesium compound $X$. $X$ reacts with dilute $HCl$ and forms $Y$.

  1. $MgO$
  2. $MgSiO _3$
  3. $SiCl _4$
  4. $MgCl _2$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
As per the given question reactions are:

$SiO _2+2Mg\rightarrow 2MgO+Si$
silica                          $X$

Again,

$MgO+2HCl\rightarrow MgCl _2+H _2O$
 $X$                                $Y$
Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Which among the following compound has the highest melting point?

  1. $\displaystyle C{ S } _{ 2 }$
  2. $\displaystyle HI$
  3. $\displaystyle { H } _{ 2 }S$
  4. $\displaystyle { H } _{ 2 }O$
  5. $\displaystyle MgO$
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

$MgO$ has highest melting point, because this is ionic in character and has very high lattice energy.
Hence, the answer is $MgO$.

Multiple choice some important compounds of magnesium and calcium the s-block elements chemistry

Among the following which is a white crystalline solid?

  1. $\displaystyle { C } _{ 3 }{ H } _{ 8 }$
  2. $\displaystyle CO$
  3. $\displaystyle Cu{ Cl } _{ 2 }$
  4. $\displaystyle { Cr } _{ 2 }{ O } _{ 3 }$
  5. $\displaystyle MgO$
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Magnesium oxide (MgO) is a white, high-melting crystalline solid used in refractories.